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Tin doped cadmium oxide (Cd1-xSnxO) thin films at different tin (Sn) concentrations (x = 0, 0.03, 0.05, 0.07) were prepared using electron beam evaporation technique and subjected to various characterisations. From XRD, prepared thin films shows polycrystalline nature with cubic structure. FE-SEM nano-graphs confirmed the elongated oval shape morphology with 1:3 aspect ratios. FT-IR analysis revealed the presence of functional groups and chemical interactions. Raman spectrum was recorded in the range of 200 cm−1 to 1000 cm−1. Using Tauc's relation optical bandgap is calculated and it is found to be increased 2.00 eV – 2.40 eV. Photoluminescence spectra were recorded Cd1-xSnxO thin films and emission peaks were found in visible region. CIE diagrams confirm the thin films in blue- green portion. Using a source meter, the electrical properties were examined and it was observed that the electrical resistivity decreased. Magnetic properties reveals that the Sn-doped CdO thin films exhibit ferromagnetic nature. [ABSTRACT FROM AUTHOR]

A serial of red-emitting MgMoO4: Eu3+ phosphors were synthesized via a high-temperature solid-phase approach. The effect of partially combined substitution of Mg2+-Mo6+-O2− with Ca2+-W6+-F− on the structure and luminescent properties of the MgMoO4: Eu3+ phosphor was thoroughly investigated. The crystal structure of the as-prepared MgMoO4: Eu3+ phosphor was not influenced by the partially combined Ca2+-W6+-F− substitution. Under the excitation of 394 nm, The MgMoO4: Eu3+ phosphor could emit bright red light centered approximately at 612 nm, corresponding to the 5D0 → 7F2 transition of Eu3+ and the optimal concentration of Eu3+ was about x = 0.10. After the partially combined Ca2+-W6+-F− substitution, the luminescence intensity of Eu3+ ions was approximately 1.94 times of the initial values owing to the alteration of the crystal field and charge compensation. The thermal stability of the partially substituted phosphor was significantly enhanced and the emission intensity at 423 K was approximately 82.3% of the initial value at room temperature. The internal quantum efficiency of the partially substituted sample is about 49.5%. A white light-emitting diode (LED) manufactured by the partially substituted red Mg0.7Ca0.2Mo0.8W0.2O3.8F0.2: 0.10Eu3+, combined with commercial blue-green phosphors and 395 nm chips exhibits high performance featuring CCT = 5441 K and Ra = 88.7. These results mean that the partially combined Ca2+-W6+-F− substitution in MgMoO4: Eu3+ can be used to optimize luminescent properties of phosphors applied in white LEDs. [ABSTRACT FROM AUTHOR]

A serial of red-emitting MgMoO4: Eu3+ phosphors were synthesized via a high-temperature solid-phase approach. The effect of partially combined substitution of Mg2+-Mo6+-O2− with Ca2+-W6+-F− on the structure and luminescent properties of the MgMoO4: Eu3+ phosphor was thoroughly investigated. The crystal structure of the as-prepared MgMoO4: Eu3+ phosphor was not influenced by the partially combined Ca2+-W6+-F− substitution. Under the excitation of 394 nm, The MgMoO4: Eu3+ phosphor could emit bright red light centered approximately at 612 nm, corresponding to the 5D0 → 7F2 transition of Eu3+ and the optimal concentration of Eu3+ was about x = 0.10. After the partially combined Ca2+-W6+-F− substitution, the luminescence intensity of Eu3+ ions was approximately 1.94 times of the initial values owing to the alteration of the crystal field and charge compensation. The thermal stability of the partially substituted phosphor was significantly enhanced and the emission intensity at 423 K was approximately 82.3% of the initial value at room temperature. The internal quantum efficiency of the partially substituted sample is about 49.5%. A white light-emitting diode (LED) manufactured by the partially substituted red Mg0.7Ca0.2Mo0.8W0.2O3.8F0.2: 0.10Eu3+, combined with commercial blue-green phosphors and 395 nm chips exhibits high performance featuring CCT = 5441 K and Ra = 88.7. These results mean that the partially combined Ca2+-W6+-F− substitution in MgMoO4: Eu3+ can be used to optimize luminescent properties of phosphors applied in white LEDs. [ABSTRACT FROM AUTHOR]

The Tb3+/Dy3+ co-doped Boro-Phosphate Glass (BPANZDyTb) was produced (40 B2O3 + 39P2O5 + 5 Al2O3 + 5 NaF + 10 ZnO + 0.5 Tb2O3 + 0.5 Dy2O3) using melt-quenching technique. X-ray diffraction measurements, Raman, and Fourier Transform Infrared were used to evaluate the structural behavior of the prepared glass. Powder-XRD spectra, in the 10–90° range showed that the prepared glass was amorphous. FTIR analysis reveals that the network contains a variety of structural groups, including B-O-B, BO4, BO, P-O, PO2, P-O-B, and PO4 units. The UV–visible diffuse reflectance spectroscopy was used to record and study the optical linear properties of Tb3+/Dy3+ co-doped Boro-Phosphate Glass (BPANZDyTb). The photoluminescence excitation peak was obtained at 348 nm. The emission peaks were located at 484 nm (4F9/2 → 6H15/2 → blue), 576 nm (4F9/2 → 6H13/2 → yellow), and 662 nm (4F9/2 → 6H11/2 → red). Tb3+ ions are located at 412 nm (5D3 → 7F5), 441 nm (5D3 → 7F4), 546 nm (5D4 → 7F5), and 625 nm (5D4 → 7F3). The result of CIE 1931 chromaticity coordinates indicate that the prepared glass is suitable material for cold white light emitting diode applications due to its color coordinates x = 0.3106 and y = 0.3240 and correlated color temperature (CCT) values about 6768 K. The gamma-ray parameters such as half-value layer (HVL), mass attenuation coefficient (μ/ρ), mean free path (MFP), and effective atomic number (Zeff) of the BPANZDyTb glass were studied using Phy-X software. The results of the gamma-ray parameter show that the Dy3+ ions and Tb3+ ions co-doped BoroPhosphate glass is an appropriate material for radiation shielding applications. [ABSTRACT FROM AUTHOR]

This study reports enhancing the emission intensity of Dy3+ doped zinc gallate phosphor via Li+ monovalent co-doping. 2–12 mol% Li+ co-doped samples and a 0.05 mol% Dy3+ doped sample were synthesized using a solid-state synthesis technique. X-ray powder diffraction was used to analyze the phase of the synthesized phosphors. By recording the reflectance, the absorption properties were quantified using Ultraviolet-Visible spectroscopy, which displayed absorption peaks corresponding to the Dy3+ activator ions. The Kubelka-Munk function was used to estimate the bandgap and its variation concerning co-dopant concentrations. Energy dispersive electron spectroscopy and field emission scanning electron microscopy have been used to analyze the individual samples' elemental composition and surface morphology. Surface mapping was also conducted using time-of-flight secondary ion mass spectrometry. X-ray photoelectron spectroscopy (XPS) was carried out for the 2 and 10 mol% Li+ co-doped samples to understand the structural properties. XPS confirmed the presence of anti-site defects in the synthesized samples. Phosphorescence spectra were recorded to analyze the effect of the Li+ co-doping on the excitation and emission, which showed a substantial increase in intensity. Apart from Dy3+ characteristic emission, all samples exhibited defect emission using a 299 nm excitation wavelength. The luminescence decay time for both types of emission spectra was recorded and found to be in microseconds. The thermoluminescence technique was used to quantify the trap states created between the valance and conduction bands. The analyzed samples were found to have more than one trap with varying trap densities and activation energies. The color chromaticity coordinates were determined for each sample regarding defect emission and the characteristic emission of the Dy3+ activator ions to assess the color of the emission generated. The information obtained shows promising possibilities that this phosphor material may be a good fit for light-emitting diodes and display technologies based on the emission wavelengths produced. [ABSTRACT FROM AUTHOR]

We present the development of multifunctional blue-emission organic light-emitting diodes (OLEDs) using TADF-exciplex materials. These OLEDs exhibit sensitivity to external stimuli and achieve a maximum external quantum efficiency (EQE) of 11.6% through partly liquid processing. This technique allows for large-scale production on arbitrary geometries. The potential multifunctionality of the devices arises from their response to low external magnetic fields (up to 100 mT) with an efficiency up to 2.5% for magnetoconductance, while maximum magneto-electroluminescence effects of 4.1% were detected. We investigated novel aspects, including the utilization of two organic materials without further doping and the investigation of the impact of 2,2ʹ,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) processing in liquid and vapor form. The insights gained provide a fundamental understanding regarding the applicability of exciplex (EX) materials for fully solution-processed OLEDs through a deliberate omission of doping. Our work represents a significant advancement on the path towards multifunctional OLED technology, with potential applications in cost-efficient, scalable organic full-color displays and advanced sensing system. [ABSTRACT FROM AUTHOR]

Charge injection and transport interlayers based on artificial green carbon materials are imperative for a sustainable future of many classes of optoelectronic devices, including organic light-emitting diodes (OLEDs). Especially, porphyrin derivatives can act as efficient energy and charge funnels mimicking their successful photosynthetic function. Here, we report on the application of a novel green carbon material, in particular, a zinc porphyrin derivative bearing an amidine functional group (referred to as ZnP-amidine), as an electron transport material in fluorescent OLEDs based on a green-yellow co-polymer emitter. ZnP-amidine is processed from environmental friendly solvents without any annealing requirements thus being suitable for low-cost sustainable optoelectronics. It is applies as an ultra-thin interlayer between the aluminum cathode and the emissive layer to enable efficient electron transport and stable performance. This work paves the path towards low-cost green carbon materials inspired by natural processes for organic optoelectronics. [ABSTRACT FROM AUTHOR]

Blue phosphorescent organic light-emitting diodes (B-PHOLEDs) using host–guest emissive layers have been studied, where the host and guest are 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) and bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrPic), respectively. For the emissive layer with dye (guest) concentration of either 3 mol% or 10 mol%, there exist both the major and minor effective bandgaps. The major effective bandgap is governed by the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) levels of 26DCzPPy, because the host molecules form a major dynamic-favorable channel to transport charge carriers. The minor effective bandgap is governed by the LUMO and HOMO levels of FIrPic, since the guest molecules form a minor thermodynamic-favorable channel to transport charge carriers. For the emissive layer with dye concentration of 22 mol%, the effective bandgap is determined by the LUMO and HOMO levels of FIrPic, because the guest molecules form a both dynamic- and thermodynamic-favorable channel to conduct charge carriers. Although the B-PHOLED with emissive layer of 26DCzPPy:FIrPic (3 mol%) shows wider exciton formation zone than the one with emissive layer of 26DCzPPy:FIrPic (10 mol%), the latter gives higher stability than the former, mostly attributed to the shorter triplet lifetime of 26DCzPPy:FIrPic (10 mol%) than that of 26DCzPPy:FIrPic (3 mol%). Due to both the larger effective bandgap and more charge carrier traps, the emissive layer of 26DCzPPy:FIrPic (10 mol%) enlarges the exciton formation zone and thereby increases device stability than that of 26DCzPPy:FIrPic (22 mol%), despite that the former has the longer triplet lifetime than the latter. The current research provides some novel insights into the correlation of dye-based nanoarchitectonics (dye concentration) with the device performance, helpful for the commercial development of B-PHOLEDs using host–guest emissive layers. [ABSTRACT FROM AUTHOR]

The family of rare-earth doped phosphors has drawn pronounced attention in technological of fingerprint visualization, anti-counterfeiting, and phosphor-converted light-emitting diodes applications. A series of NaSrGd(1–x–y)EuxDyy(WO4)3 powder luminescent materials were synthesized by a solid-state reaction. The emission color of NaSrGd(WO4)3:Dy3+ phosphor could be tunned via changing concentrations of Eu3+ ion. In addition, the phosphors exhibit narrow red-light emission at 610 nm caused by the electric dipole transition 5D0 → 7F2 of Eu3+. Especially, the phosphor exhibits superior thermal stability, its emission intensity of optimum sample remained ± 15% over the temperature range from 233 to 393 K. The Commission International de I'Eclairage (CIE) chromaticity coordinates of x = 0.4 are (0.6388, 0.3371) with a high color purity (92.84%). More importantly, prepared color-changing device of phosphors achieves a high level of optical safety. The results demonstrate that their materials can be potentially applied to the field of white light-emitting diodes (LEDs) and optical anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Lead halide perovskite quantum dots (PQDs) have demonstrated extremely excellent optical properties and great application potential in various optoelectronic devices. However, it is still a challenge to maintain both stability and multipeak emission performance for PQDs. In this work, we successfully synthesize multipeak emission CsPbCl1.5Br1.5:Eu3+–SiO2 PQDs employing molecular sieves through high-temperature solid-state reactions, and the energy transfer process is designed to enhance the emission of Eu3+. The excellent thermal stability of as-prepared PQDs has also been proved by thermal cycle test from 25 to 100 °C. Furthermore, the as-prepared doped PQDs are utilized for white light emitting diodes, which show excellent white light performance. The material is expected to be applied as a component on high-quality white LED devices, and our finding is believed to offer a new strategy for designing multipeak emission PQDs. [ABSTRACT FROM AUTHOR]

In this report, we present luminescent properties of a composite based on zinc sulfide quantum dots (ZnS QDs) in a SiO2 matrix, doped with different concentrations of Eu3+ ions and with different thermal treatments in order to obtain white light and a tunable emitting phosphor. Various complementary techniques have extensively studied the evolution of effects of thermal treatment and Eu3+ doping on the crystallinity and emission properties. Transmission electron microscopy certifies the formation of undoped ZnS powder of particles with sizes of approximately 4.6 nm, combined with XRD, shows the amorphous nature of the matrix host as well as the presence of embedded crystalline nanoparticles. The incorporation of the Eu3+ dopant does not produce a significant effect in the crystalline structure of the ZnS@SiO2 composite. Raman spectroscopy results indicate that thermal treatment induced to formation cristobalite-low and Zn2SiO4. The photoluminescence measurements indicated that ZnS@SiO2 nanocomposite exhibit an intense and wide blue emission band centered at around 440 nm under 325 nm excitation, which is modified by the temperature, with the enhancement of the intensity, widening of the band emission, as well as maximum shifting. The calculations of the CIE 1931 chromaticity coordinates show the tuning of the tonality of the emission color from blue to cold white light, these results strengthened the possibility that the prepared samples could be applied as an efficient phosphor in the visible range. [ABSTRACT FROM AUTHOR]

The determination to develop high-speed, efficient and versatile micro/nano photonic systems has inspired vast studies on photonic circuits. We demonstrate here a near-ultraviolet (NUV) monolithic multicomponent integrated circuit on Si substrate, including two non-suspended multiple quantum wells diodes (MQW-diodes) and an arc-shape waveguide. The two MQW-diodes which are fabricated by the same process can function as emitter and detector, respectively, and their roles can be switched with each other, because the InGaN/GaN multiple quantum wells, which are employed in the emitter to produce near-ultraviolet light, are also utilized by the detector for photodetection. The arc-shape waveguide which serves as a communication channel between the emitter and the detector can change the light propagation direction by 90°. Due to light confinement structure of the wafer, silicon removal and back GaN etching is avoided, which makes the devices more robust, as well as simplifying the processing flow. Two MQW-diodes can communicate with each other at 100 Mbps via the arc-shape waveguide, and the light signals of 200 Mbps from the emitter can also be detected by a commercial photodiode module via free space, which forms a three-dimensional NUV light communication system. This work paves the way toward comprehensive photonic integration for wide variety of potential applications. [ABSTRACT FROM AUTHOR]

The fluorescent ceramic GdAG:Ce was formed by aqueous tape casting-isostatic pressing process and synthesized by high temperature solid state method. To investigate the effect of introduction of Gd3+ on the crystal structure, the photoluminescence (PL) properties, decay lifetime and the white light-emitting diodes (WLED) applications, non-Gd3+ analogue sample YAG:Ce was prepared as well. In contrast, fluorescent ceramic GdAG:Ce exhibited a relatively smaller XRD peaks, much stronger PL emission intensity and shorter lifetime than that of YAG:Ce. These findings could be beneficial to the improvement of the WLED performance. Moreover, fluorescent ceramic GdAG:Ce was made up of practical with garnet structure, which possessed good thermal stability. As a consequence, an increase of color rendering index (Ra) to 62.3 and decrease of correlated temperature (CCT) to 3208 K was achieved by the WLED device based on fluorescent ceramic GdAG:Ce. The impressive results provided a basis for the fluorescent ceramic used in the field of WLED with high Ra and low CCT. [ABSTRACT FROM AUTHOR]

In this study, a flexible graphene microsensor with an embedded microheater was fabricated for nitrogen monoxide (NO) detection. The microsensor and heater were fabricated on a polyethylene terephthalate (PET) substrate through picosecond laser ablation. The results of this study indicated that sensor temperature could be precisely and quickly controlled by adjusting the driving voltage of the microheater. The NO recovery time decreased from 1520 to 283 s (a drastic reduction of 81%) as the sensor temperature increased from 20 to 100 °C. Under ultraviolet (UV) irradiation, the recovery time decreased with the increase in input power of the LEDs. The recovery time decreased by 78% when the distance was 5 mm. In addition, the light-activation of UV-C light-emitting diodes (LED) revealed the promising gas sensing characteristics and visualized their possibility and capabilities. Furthermore, the gas sensor exhibited outstanding durability during cyclic bending tests. An increase in the bending angle decreased sensor response and increased NO recovery time, because sensor deformation influenced sensor conductivity. This study demonstrated the picosecond laser technique to the fabricated flexible graphene microsensor with the heating rate and UV-C irradiation, helping to design next-generation advanced devices for gas detection. [ABSTRACT FROM AUTHOR]

Despite the dominance in consumer electronics, the use of group-IV semiconductors and their heterostructures is still limited for photonic devices, attributed to the poor emission quantum efficiency in Si and Ge due to their indirect bandgap nature. This has posed serious bottlenecks towards the rapid progress of integrated silicon photonics. However, the recent advances of low-dimensional Si-based heterostructures have shown enormous potential in this direction owing to the significant modification of band structures, leading to improved optical and electronic properties over their bulk counterparts. In this regard, one dimensional Si and Ge nanowires have witnessed an explosion of research interests because of their potential in several promising applications for ultra-compact, silicon-compatible, and functional optoelectronic devices. Novel device architectures integrated with single nanowires and nanowire array geometries have been actively studied and developed. This review presents recent advances in the study of group-IV semiconductor nanowires and their heterostructure-based photonic devices like photodetectors, solar cells and light-emitting diodes etc. Several novel but rational device designs are presented and discussed here, from single nanowire for extraordinary performance to nanowire array heterostructures for large area applications. [ABSTRACT FROM AUTHOR]

Beginning with our exciting discovery of germanium (Ge) spherical quantum-dot (QD) formation via the peculiar and symbiotic interactions of Si, Ge, and O interstitials, we have embarked on a journey of vigorous exploration, creating unique configurations of self-organized Ge-QDs/Si-containing layers. Our aim is to generate advanced Ge-QD photonic devices, while using standard, mainstream Si processing techniques. This paper summarizes our portfolio of innovative Ge-QD configurations. With emphasis on both controllability and repeatability, we have fabricated size-tunable, spherical Ge-QDs that are placed at predetermined spatial locations within Si-containing layers (SiO2, Si3N4, and Si) using a coordinated combination of lithographic patterning and self-assembled growth. We have successfully exploited the multi-dimensional, parameter spaces of process conditions in combination with layout designs to achieve exquisite control available through the thermal oxidation of lithographically patterned, poly-Si1 − xGex structures in close proximity with Si3N4/Si layers. In so doing, we have gained insight into the growth kinetics and formation mechanisms of self-organized, Ge spherical QDs embedded within SiO2, Si3N4, and Si layers, respectively. Our Ge-QD configurations have opened up a myriad of process/integration possibilities including top-to-bottom evanescent-wave coupling structures for SiN-waveguided Ge-QD photodetectors and Ge-QD light emitters for Si photonics within Si3N4 integrated photonics platforms for on-chip interconnects and sensing. [ABSTRACT FROM AUTHOR]

A series of Mn2+-doped solid Zn3Ga2GeO8 materials with far-red broad-band emissions is prepared as promising candidates for light emitting diodes (LEDs) for application in indoor plant cultivation. Phosphor exhibits broad far-red emissions, ranging from 600 to 1100 nm which overlap with the absorption range of the phytochrome ( P fr ). In addition, the co-doping with Ca2+ contributes a 1.57-fold increase in the far-red-emission intensity at room temperature. Encapsulating phosphor onto ultraviolet LED chips yields far-red-emitting LED devices, which can be promising candidates for promoting indoor plant cultivation. [ABSTRACT FROM AUTHOR]

Pure In2O3 and mixed Mn2O3–In2O3 nanomaterials were synthesized via vapor transport method. The X-ray diffraction patterns demonstrated the cubic crystalline phase for pure In2O3 sample, whereas a combination of cubic In2O3 and orthorhombic Mn2O3 phases were observed for the mixed sample. The scanning electron microscopy images revealed the formation of randomly oriented nanorods for pure In2O3 sample, while assemblies of nanorods with different lengths and diameters were reported for the mixed sample. The transmittance spectrum of pure In2O3 was greater than 80% over the visible spectral range, while the transmittance of the mixed Mn2O3–In2O3 nanostructured film was 32%. The obtained band gap values for pure In2O3 and mixed Mn2O3–In2O3 nanostructured thin films were 3.92 and 3.37 eV, respectively. The mixed Mn2O3–In2O3 nanostructured thin film has higher refractive index, higher optical conductivity, and lower electrical resistivity than those for pure In2O3 film. Two obvious emission peaks were observed for the pure and the mixed samples. The photoluminescence intensity of the mixed Mn2O3–In2O3 nanostructured thin film is higher than that of pure In2O3 indicating its validity to be used in optoelectronic applications such as light-emitting diodes. [ABSTRACT FROM AUTHOR]

A SiO2-coated LiAlSiO4:18 mol%Eu3+ (LASE) phosphor was prepared via the high-temperature solid-state reaction method and the sol–gel process. The crystal phase, surface morphology, luminescent properties, and thermal stability of the coated phosphor were investigated and compared with those of uncoated phosphor. SiO2 forms a transparent dense film on the phosphor surface without changing the crystal phase and the peak positions of the fluorescence spectra. After coating SiO2, the lifetime of the optimal LASE@5wt%SiO2 phosphor has a slight change, but its luminescence intensity, thermal stability, and color purity are enhanced by 9.3%, 19%, and 90%, respectively. And its CIE chromaticity coordinate is calculated to be (0.6460, 0.3514), close to the National Television System Committee (NTSC) value (0.67, 0.33). The fabricated white light-emitting diode (w-LED) device using the combination of a 395 nm InGaN chip and phosphors mixture (BaMgAl10O17:Eu, SrSi2O2N2:Eu and the optimized LASE@5wt%SiO2 phosphors) can emit a bright white light with good CIE color coordinates (0.3265, 0.3783), low correlated color temperature (CCT) of 5720 K, and high color rendering index (CRI) of 89.3. All the results demonstrate that the optimized phosphor can be potentially used as a red phosphor in near-ultraviolet (n-UV) excited w-LEDs. [ABSTRACT FROM AUTHOR]

This paper describes the fabrication of heteromorphic microlens arrays in the polymethyl methacrylate/titanium/organically modified siloxanes photosensitive hybrid films by UV nanoimprint technique and the applications of the prepared microlens arrays on the organic light-emitting diode. The hybrid films were obtained by combining a sol–gel technique and spin coating method. UV–visible spectroscopy and atomic force microscope are used to characterize the properties of the hybrid films, and the results indicate that the hybrid films have high transmittance and small surface roughness. Scanning electron microscope and surface profile results show that the heteromorphic microlens arrays formed in the hybrid films are uniform and well defined. Optical microscopy results show that the hexagonal microlens arrays have the relatively strong focusing ability and excellent imaging performance. Finally, the microlens arrays are applied to the organic light-emitting diode, the luminous properties of the organic light-emitting diode is enhanced, and there is a maximum improvement of about 43.9% in current efficiency for OLEDs with hexagonal microlens arrays. All the results above indicate that it is a simple and low-cost process to fabricate hybrid film microlens arrays by UV nanoimprint technique, and the prepared microlens arrays have potential applications in the organic light-emitting diode. [ABSTRACT FROM AUTHOR]

The optoelectronic characteristics of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with quaternary last quantum barrier (QLQB) and step-graded electron blocking layer (EBL) are investigated numerically. The results show that the internal quantum efficiency (IQE) and radiative recombination rate are remarkably improved with AlInGaN step-graded EBL and QLQB as compared to conventional or ternary AlGaN EBL and last quantum barrier (LQB). This significant improvement is assigned to the optimal recombination of electron–hole pairs in the multiple quantum wells (MQWs). It is due to the decrease in strain and lattice mismatch between the epi-layers which alleviates the effective potential barrier height of the conduction band and suppressed the electron leakage without affecting the holes transportation to the active region. Moreover, to figure out quantitatively, the electron and hole quantity increased by ~ 25% and ~ 15%, respectively. Additionally, the IQE and radiative recombination rate are enhanced by 48% and 55%, respectively, as compared to conventional LED. So, we believe that our proposed structure is not only a feasible approach for achieving highly efficient DUV LEDs, but the device physics presented in this study establishes a fruitful understanding of III nitride-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Whitlockite β-Ca3(PO4)2-type materials have multiple crystallographic sites for occupying by rare earth ions to achieve a strong and broadband emitting covering the spectra from cyan to deep red and various abundant heterogeneous substitution ability to develop new luminescent materials. In this work, a broadband emitting Sr8MgGa(PO4)7:Eu2+ (SMGP) phosphor, deriving from β-Ca3(PO4)2 host by cations substitution, was prepared by solid state reaction at high temperature. Based on the Rietveld refinement results, SMGP host possesses a monoclinic system with a space group C2/m. The optimized doping concentration was determined to be 0.04. The SMGP: 0.04Eu2+ sample exhibit strong absorption at the wavelength of 250–500 nm, and a broadband emission from 450 to 800 nm covering the spectra from cyan to deep red. However, the SMGP: 0.04Eu2+ phosphors exhibit poor thermal stability with activation energy as 0.156 eV. By adjusting the composition of the trivalent ions Ga3+/Lu3+, controllable emission color from green to yellow can be achieved in the Sr8MgGa1-xLux(PO4)7:Eu2+ solid solution phosphors. Finally, a white light-emitting diodes (LED) lamp was prepared by coating the mixtures of SMGP: 0.04Eu2+ phosphors and BaMgAl10O17:Eu2+ phosphors on the surface of 400 nm near-ultraviolet chip. The optimized white LED lamp exhibits a correlated color temperature of 2991 K and a good color rendering index of 90.2. These results demonstrate the commercialized prospect of SMGP: Eu2+ materials as a broadband emitting phosphor for application in solid state lighting. [ABSTRACT FROM AUTHOR]

Red light-emitting CdTexSe(1−x) quantum dots (QDs) were synthesized as a new red phosphor for light-emitting diodes. CdTexSe(1−x) QDs were characterized through X-ray diffraction, high-resolution transmission electron microscopy, photoluminescence spectroscopy, and UV–Vis absorption spectroscopy. Results revealed that red-emitting CdTexSe(1−x) QDs were highly crystalline and had good optical properties. A red LED device was fabricated by combining red light-emitting CdTexSe(1−x) QDs as the phosphor with a near-UV InGaN LED chip as the excitation source. The CIE color coordinates of the red LED at (0.6778 and 0.3106) when the reflux time was 1 h. Therefore, CdTexSe(1−x) QDs are good candidates for LED applications. [ABSTRACT FROM AUTHOR]

In this paper, transparent conducting n-type ZnO:Ga and commercially available SnO 2 :F (U-type Asahi) thin films have been used as a front electrode (Anode) in organic light-emitting diode (OLED)-based display devices. RF magnetron sputtered ZnO:Ga thin films with an electrical resistivity of 9.6 × 10 - 5 Ω - c m , low sheet resistance less than 5.6 Ω / □ and optical transparency greater than 90% have been reported at room temperature (RT) using the glass substrate. The OLED device structure consists of transparent conducting oxide (TCO) (170 nm)/HAT-CN (15 nm)/TAPC (30 nm)/CBP:Ir(ppy) 3 (30nm; 8wt%)/BPhen(50 nm)/LiF (1 nm)/Al (120 nm). Normalized intensity of both types TCO (ZnO:Ga and SnO 2 :F)-based OLED shows a similar kind of result. The results suggest that Ga-doped ZnO thin films are the substitutional anode materials of commercially established SnO 2 :F (fluorine-doped tin oxide), ITO (tin-doped indium oxide) for the OLED application, and also in other optoelectronic devices. The important figures of merit such as external quantum efficiency, current and power efficiency of ZnO:Ga (GZO)-based OLED are demonstrated and compared with SnO 2 :F (FTO)-based OLED. These results suggest that Ga-doped ZnO thin films can be a promising candidate as the anode layer in OLEDs as a substitution to ITO and SnO 2 :F film. [ABSTRACT FROM AUTHOR]

In this paper, a novel structure is presented in order to decrease the polarization charges of quantum wells. The main purpose of this design is to make electron and hole wavefunctions closer to each other and to increase overlap integral following an increase of radiative recombination rates and internal quantum efficiency. Furthermore, carriers will be increased and become more balanced and identical which leads to an increase in efficiency of light-emitting diodes. The improvement of radiative recombination rates is studied in new structures. Energy bands diagram, carriers density, current density–voltage, and power density–current density are used to demonstrate the superior performance of the proposed structures and to find the optimal point. The carriers density diagrams for conventional and new structures reveal an increment in carriers injection in new structures. The radiative recombination rates diagram of the proposed structures also indicates that all potential wells participate in light emission. [ABSTRACT FROM AUTHOR]

In this work, the upconversion temperature sensing was used to study the light-emitting properties of Gd2(MoO4)3:Y3+/Yb3+/Er3+-based LED. In order to obtain high-intensity upconversion luminescence, we studied the effect of Y3+ doping concentration on the photon upconversion of Yb3+/Er3+-activated Gd2(MoO4)3 under 940 nm excitation. We also explored the calibration of upconversion temperature sensing and established a reliable temperature scale. Finally, the light-emitting properties of an operating LED that consisted of a 940-nm semiconductor chip and the optimum phosphor were studied by using the upconversion luminescence thermometry. [ABSTRACT FROM AUTHOR]

Eu3+-doped germanate based red emitting phosphors SrGe4O9: xEu3+ (0 ≤ x ≤ 0.5 mol%) were prepared by high-temperature solid-state procedure. Moreover, the Density Functional Theory (DFT) calculation, X-ray diffraction (XRD) Rietveld refinement, scanning electron microscopy (SEM), and photoluminescence (PL) measurement were discussed in detail to fully investigate the crystal structure and PL properties of SrGe4O9: xEu3+. Furthermore, the Judd–Ofelt (J–O) analysis demonstrated that the Eu3+ ions in the SrGe4O9 host possessed lower sites symmetry. In addition, the phosphor SrGe4O9: 0.35%Eu3+ displayed superior thermal stability with PL intensity at 423 K is around 90% of its initial value at 298 K. As a result, the white light emitting diodes (WLED) device based on SrGe4O9: 0.35%Eu3+ achieved an expected result of a correlated color temperature (CCT) of 4573 K and a color rendering index (CRI) of 80.8 under a voltage of 3 V and a driven current of 20 mA. [ABSTRACT FROM AUTHOR]

The work in this paper is the first report on the green synthesis of the blue light emitter from waxy, flammable solid collected from Cinnamomum camphora by controlled combustion for photonic applications. Analysis with field emission scanning electron microscope and high-resolution transmission electron microscope provides the morphology, whereas the thermogravimetric analysis gives the thermal stability of the soot. The optical and structural characterizations are done by recording UV-Visible, Photoluminescent, and Raman Spectrum. The CIE plot and the power spectrum of the sample show a blue emission at an excitation of 350 nm at room temperature with a quantum yield of 46.15%. The dependence of luminescent behavior on temperature and excitation wavelength reveals that the material is a tunable blue emitter. This green synthesis of the blue light emitter is highly significant, when the world is in search of a simple, phosphor-free, non-toxic, cost-effective material with good quantum efficiency. [ABSTRACT FROM AUTHOR]

The light-emitting-diode (LED) surface of GaN epilayers grown on Si substrate was irradiated by a femtosecond laser ( λ = 800 nm). The morphology of LED surface after laser irradiation was measured by optical microscope and scanning electron microscopy. It was found that many radial cracks appeared in the film on account of thermal expansion and then became more numerous as the number of laser pulses increased. In addition, the changes of the micro structure of GaN and Si substrate were studied by means of Micro Raman Spectroscopy. The results showed the presence of polycrystalline silicon and the decomposition of GaN had taken place in the laser spot or the region with the large laser fluence. Comparatively, in the areas with the low laser fluence or the edge of laser spot, the characteristic peaks of GaN films and the AO phonon peak of Si had an obvious blueshift, which most likely was the result of compressive stress between GaN layers and Si substrate. The maximum values of the compressive stress were 0.74 GPa and 1.4 GPa, respectively. Furthermore, with the increase of the laser fluence, the original Si crystalline structure recovered gradually. The above study showed that the stress, the transformation and the deformation play a predominant role in the femtosecond laser etching process of LED. [ABSTRACT FROM AUTHOR]

A series of novel red-emitting phosphors CaLa(PO): xEu were synthesized by high-temperature solid state reactions. The photoluminescence excitation and photoluminescence spectra of these phosphors were investigated in detail. O-Eu charge transfer band peaking at about 261 nm is dominant in the PLE spectra of Eu-doped CaLa(PO), indicating that the phosphors are suitable for tricolor fluorescent lamps. The phosphors also show a good absorption in near ultraviolet (around 395 nm) and blue (around 465 nm) spectral region, which indicates that it can be pumped with NUV and blue chips for white light-emitting diodes. The transition of D → F of Eu in this lattice can emit bright red light. CaLa(PO) could accommodate a large amount of Eu with an optimal concentration of 60 mol%. The dipole-dipole interaction between Eu is the dominant mechanism for concentration quenching of Eu. The calculated color coordinates lie in red region ( x = 0.64, y = 0.36), which is close to YO: 0.05Eu ( x = 0.65, y = 0.34). The integral emission intensity of CaLa(PO): 0.6Eu is 1.9 times stronger than that of widely used commercial red phosphor YO: 0.05Eu. All these results indicate that Eu-doped CaLa(PO) is a promising red-emitting phosphor which can be used in tricolor fluorescent lamps and white light-emitting diodes . [ABSTRACT FROM AUTHOR]

NPB usually is used as a hole-transport layer in OLED. In fact, it is a standard pure blue-emission material. However, its light-emitting efficiency in OLED is low due to emissive nature of organic material. Herein, a deep-blue OLDE based on NPB was fabricated. The light-emitting efficiency of the device demonstrates a moderate value, and efficiency roll-off is little under high current density. The device demonstrates that the electroplex's emission decreases with increasing electric field intensity. [ABSTRACT FROM AUTHOR]

Moreover, at the end of third paragraph in "4.1 SiN-embedded Ge-QD microdisk light emitters", unnecessary "Ge QD SiN silicon oxide air" has been remained. Thanks to the high absorption coefficients and pseudo-direct band-gap properties of Ge near the C-band communication wavelengths, active photonic devices (light sources and photodetectors) in Si PICs are enabled [2, 3] with small form factors on 2-D silicon-on-insulator (SOI) platforms. [Extracted from the article]

A multispectral, multidirectional, portable and dome-shaped acquisition system is developed within the framework of the research projects RICH (KU Leuven) and EES (RMAH, Brussels) in collaboration with the ESAT-VISICS research group (KU Leuven). The multispectral Portable Light Dome (MS PLD) consists of a hemispherical structure, an overhead camera and LEDs emitting in five parts of the electromagnetic spectrum regularly covering the dome's inside surface. With the associated software solution, virtual relighting and enhancements can be applied in a real-time, interactive manner. The system extracts genuine 3D and shading information based on a photometric stereo algorithm. This innovative approach allows for instantaneous alternations between the computations in the infrared, red, green, blue and ultraviolet spectra. The MS PLD system has been tested for research ranging from medieval manuscript illuminations to ancient Egyptian artefacts. Preliminary results have shown that it documents and measures the 3D surface structure of objects, re-visualises underdrawings, faded pigments and inscriptions, and examines the MS results in combination with the actual relief characteristics of the physical object. Newly developed features are reflection maps and histograms, analytic visualisations of the reflection properties of all separate LEDs or selected areas. In its capacity as imaging technology, the system acts as a tool for the analysis of surface materials (e.g. identification of blue pigments, gold and metallic surfaces). Besides offering support in answering questions of attribution and monitoring changes and decay of materials, the PLD also contributes to the identification of materials, all essential factors when making decisions in the conservation protocol. [ABSTRACT FROM AUTHOR]

Tunable white light was realized in samples BaTiPO:2 xEu ( x = 0-0.80) by introducing orange-red light emitting Eu in self-activated blue-green light emitting matrix BaTiPO. The sample BaTiPO:2 xEu is a multiphase system consisting of BaTiPO, EuPO and TiO when x is greater than or equal to 0.20. The tunable light from blue-green to bluish-white, to white, and eventually to pinky-white of samples BaTiPO:2 xEu under UV light excitation is attributed to the light mixture of tunable blue-green light from Ti-O charge transfer transition in BaTiPO and orange-red light from Eu 4f-4f transition mostly in EuPO. The Commission International de l'Eclairage chromaticity coordinates, correlated color temperature and color rendering index were tuned from (0.262, 0.339), 9492 K and 74 for matrix sample BaTiPO to (0.324, 0.346), 5876 K and 87 for sample BaTiPO:2 xEu ( x = 0.40) under UV light excitation. Therefore, a kind of promising UV-excited white light emitting multiphase phosphor was obtained. [ABSTRACT FROM AUTHOR]

Selective laser lift-off of GaN from a sapphire substrate was demonstrated using 266-nm diode-pumped solid-state laser irradiation. To fabricate a single GaN light-emitting diode (LED) with a size of 100 μm × 100 μm, we used a simple direct scanning technique with a defocused beam and investigated the lift-off parameter in terms of the intensity. Two processing windows corresponding to lower- and higher-intensity regimes were observed experimentally. In the lower-intensity regime, the larger beam size worked better than with the higher regime. Although fluence is generally explained as a processing condition, the total input fluence for a single LED was not crucial to lift-off in case of the scanning technique using a defocused laser beam. However, an intensity of ~37 kW/cm was required to initiate the thermal decomposition reaction in GaN at any sample position. [ABSTRACT FROM AUTHOR]

The performance of inverted organic light-emitting diodes (IOLEDs) has been improved based on MoO-doped N,N′-bis-(1-naphthyl)-diphenyl-1,1′-biphenyl-4,4′-diamine (2:1 NPB:MoO in mass ratio) and 4,4′-N,N′-dicarbazole-biphenyl (2:1 CBP:MoO in mass ratio). The sandwiched- p-doped-layer hole injection structure of CBP:MoO 10 nm/NPB:MoO 5 nm/CBP:MoO 5 nm/Al showed increased device performance via enhancing hole current into the CBP, compared to the single- p-doped-layer hole injection structure of CBP:MoO 20 nm/Al, mostly due to the higher conductivity of NPB:MoO than that of CBP:MoO; it also improved device current and thereby performance than the double- p-doped-layer hole injection structure of CBP:MoO 10 nm/NPB:MoO 10 nm/Al, mostly attributed to that the hole injection from Al to CBP:MoO was more efficient than that from Al to NPB:MoO. The current research provides some insights in reducing the power loss toward the commercialization of IOLEDs. [ABSTRACT FROM AUTHOR]

We developed a visible silicon light-emitting diode (Si-LED) with a lateral p-n homojunction using dressed-photon-phonon (DPP)-assisted annealing. The lateral p-n homojunction was fabricated in order to decrease the absorption loss inherent in light emission with a photon energy higher than the band-gap energy of the material. The fabricated Si-LED emitted light in the entire visible range, including the three primary colors. The light extraction efficiency of the Si-LED was estimated to be 7.8 times higher than that of a conventional LED structure with a vertical p-n homojunction. Owing to the efficient light extraction, we clearly observed two novel features in the electroluminescence (EL) spectrum: a nonlinear increase in the EL intensity with the injected forward current, and an emission peak at 2.7 eV, at which there is no singular point in the electronic structure. From these features, we concluded that the EL from the Si-LED originated from the phonon-assisted radiative recombination of carriers with much higher energy than that of the bottom of the conduction band, via DPPs. [ABSTRACT FROM AUTHOR]

This paper reports the fabrication of a polarization-controlled infrared LED fabricated by dressed-photon-phonon (DPP)-assisted annealing of a bulk Si crystal. For the DPP-assisted annealing, linearly polarized infrared light with a wavelength of 1.342 μm was made normally incident on the top surface of the crystal. The photon energy at the peak of the emitted light spectrum of the fabricated LED was close to that of the light irradiated during the DPP-assisted annealing. A degree of polarization of as large as 0.07 was obtained. The spatial distribution of the doped B atoms in the fabricated LED was measured, and the following findings were obtained: (1) B atoms formed pairs in which the separation between the two B atoms was three times the lattice constant of the Si crystal; and (2) the B atom pairs were apt to orient along the direction perpendicular to the propagation direction and to the polarization direction of the light irradiated during the DPP-assisted annealing. Based on these findings (1) and (2), photon breeding was confirmed with respect to photon energy and spin, respectively. [ABSTRACT FROM AUTHOR]

Using the two-level two-state model, we analyzed the characteristics of enhanced electroluminescence intensity from a GaP LED fabricated by dressed-photon-phonon-assisted annealing. In this model, we utilized the fact that the adiabatic potential barrier of the electronic excited level in configuration space is lower than that of the ground level. It was confirmed by experiments that, in an actual excited level, the barrier was reduced to 0.48 eV. From this finding, it was shown that the spatial distribution of Zn atoms can be changed by means of current injection and light irradiation even at room temperature. In addition, we showed that a structure that is suitable for light emission via DPPs is formed by means of a transition between a low-barrier excited level and a high-barrier ground level, due to stimulated emission. Also, regarding the optimized conditions for maximizing the effect of DPP-assisted annealing, it was found that the optimum ratio of the number of injected electrons to the number of irradiated photons is close to 1, and this was confirmed experimentally. [ABSTRACT FROM AUTHOR]

Graphene is a highly attractive candidate for implementation as electrodes in next-generation large-area optoelectronic devices thanks to its high electrical conductivity and high optical transparency. In this study, we show all-solution-processed quantum dot-based light-emitting devices (QD-LEDs) using graphene mono- and multilayers as transparent electrodes. Here, the effect of the number of graphene layers (up to three) on the QD-LEDs performance was studied. While the implementation of a second graphene layer was found to reduce the turn-on voltage from 2.6 to 1.8 V, a third graphene layer was observed to increase the turn-on voltage again, which is attributed to an increased roughness of the graphene layer stack. [ABSTRACT FROM AUTHOR]

In this paper, we designed and simulated InGaN/AlGaN-based near-ultraviolet light-emitting diode (NUV LED) epi-structures to obtain high internal quantum efficiency and low efficiency droop. When the conventional epi-structure of an $$\hbox {Al}_{0.1}\hbox {Gal}_{0.9}\hbox {N}$$ last quantum barrier and an $$\hbox {Al}_{0.21}\hbox {Gal}_{0.79}\hbox {N}$$ electron blocking layer (EBL) was replaced with a graded last quantum barrier and multi-step EBLs, the NUV LED showed 35 % higher internal quantum efficiency and 25 % more suppression of efficiency droop than the conventional NUV LED. Furthermore, a detailed study of the grading effect of the EBL revealed that 10-step EBLs increase performance when compared to other structures. These results are attributed to the polarization-induced effect, which reduces the electron leakage and increases the hole injection efficiency. [ABSTRACT FROM AUTHOR]

In this study, a new design on last quantum barrier (LQB) is investigated numerically with the purpose of improving the optical performance of InGaN light-emitting diodes (LEDs). Through the analysis of the energy band diagrams, electrostatic fields, carrier concentrations, carrier current densities, and radiative recombination rates, we have got the simulation results that the proposed undoped-InGaN/AlInGaN superlattice (SL) LQB can significantly improve the output power and internal quantum efficiency, which is mainly attributed to the successful improvement in hole injection efficiency and suppression of electron current leakage. Moreover, the efficiency droop of the LEDs is improved slightly by using u-InGaN/AlInGaN SL as last barrier. [ABSTRACT FROM AUTHOR]

In this work, the AlGaN/AlGaN superlattices (SLs) electron blocking layer (EBL) is designed to replace conventional AlGaN EBL in the AlGaN-based deep-UV light-emitting diodes (DUV-LEDs). The simulation results show that the DUV-LEDs with SLs possess higher emission power and internal quantum efficiency as compared to those with conventional EBL, which is attributed to the suppression of electron leakage and the enhancement of hole injection efficiency due to the alleviated strain force and the appropriately modified energy band caused by SLs EBL. The results also demonstrate that the efficiency droop is markedly reduced when the SLs EBL is adopted. [ABSTRACT FROM AUTHOR]

The advantages of AlGaN-based ultraviolet light-emitting diode with AlGaN/AlGaN multi-quantum last barrier (MQLB) are investigated numerically in this work. The light output power, internal quantum efficiency, energy band diagrams, carrier concentrations, radiative recombination rate, and spontaneous emission spectra in the multi-quantum wells are investigated. The simulation results show that the structure with MQLB exhibits higher output power and smaller efficiency droop at high current as compared to the conventional one. Based on the numerical simulation and analysis, these improvements on the device characteristics are attributed to the remarkable improvement of the hole injection efficiency from p-type region, which results from the lower effective barrier height for hole transportation, the lower consumption of holes in the p-side, and the very low hole population in MQLB region. [ABSTRACT FROM AUTHOR]

Eu- and/or Mn-activated CaNaY(PO)F phosphors have been prepared via a combustion-assisted synthesis route. The powder X-ray diffraction measurement revealed that CaNaY(PO)F crystallized in a hexagonal crystal system with the space group P6/m (176). The photoluminescence spectrum of the Eu single-doped phosphor shows a broad blue emission band peaking at 451 nm under the excitation of UV irradiation. The Eu-/Mn-codoped phosphors show a blue emission band and an orange emission band, and the corresponding CIE coordinates intuitively indicate the tunable colors from blue to yellow area. The energy transfer from the Eu to Mn ions is demonstrated to be a quadrupole-quadrupole mechanism in terms of the experimental results and analysis of PL spectra and decay curves of the phosphors. The developed phosphors can be efficiently excited in the UV region and exhibit a tunable white-light emission, making them attractive as single-component white-light-emitting conversion phosphors for UV-based white LEDs. [ABSTRACT FROM AUTHOR]

The p-electrode of blue light-emitting diodes (LED) chips has a low transmittance on the blue light spectrum. The blue light emitted from the quantum wells under the p-electrode will be severely absorbed by p-electrode, which cause a decrease in blue light extraction efficiency (LEE). In this study, we first designed a current blocking layer (CBL) structure with the blue light reflection through the simulation software. The simulation results show that this structure can effectively improve blue LEE, and then, this structure was verified by experiment. Electroluminescence measurement results show that LED with Metal-distributed Bragg reflector (M-DBR) CBL exhibited better optical performance than the LED with SiO CBL and DBR CBL. It was found that M-DBR CBL can effectively increase the blue light reflectivity and prevent the light absorption from the metal p-electrode to improve LED' blue LEE. [ABSTRACT FROM AUTHOR]

An InGaN light-emitting diodes with a leakage electron recombination (LER) quantum well have been proposed and investigated numerically by using the APSYS simulation software. The simulation results indicate that the AlGaN electron blocking layer inserted between the last two quantum wells changed the carrier concentrations distribution, and the leakage electrons can be further recombined with holes in the LER quantum well which can decrease the electrons that spill out from active region. As a result, the internal quantum efficiency and light output power are markedly improved attributed to LER quantum well. [ABSTRACT FROM AUTHOR]

A novel phosphor, Mn doped LaLiTaO, was developed by solid-state reaction method. The luminescent spectra and emission efficiencies of LaLiTaO:Mn ( x = 0.001, 0.003, 0.005 and 0.01) were discussed. The effects of co-doped charge compensation ions, M = Mg, Ca, Na, were investigated, respectively. The excitation spectra indicated that LaLiTaO:Mn could be effectively excited by both NUV light and blue light. The emission spectra of the phosphor exhibit a broadband ranging from 670 to 720 nm with the maximum at about 709 nm in deep red region. The co-doping of Mg could significantly improve the luminescent properties of LaLiTaO:Mn. Thus, phosphor LaLiTaO:Mn, Mg can serve as a key component to improve color rendering of blue-chip white-LEDs. [ABSTRACT FROM AUTHOR]

We have synthesized ZnO nanocrystals, such as nanowires, nanorods, and nanosheets, using a nanoparticle-assisted pulsed laser deposition (NAPLD) method. Recently, we achieved position-controlled growth of the ZnO nanocrystals by means of a ZnO buffer layer and laser irradiation without any catalyst. The periodic structure was formed on the ZnO buffer layer by multi-beam interference patterning, and then vertically aligned ZnO nanowalls, corresponding to the patterning, were grown on the buffer layer. It was found that the periodic ZnO nanowalls grew along the c-axis direction by X-ray diffraction measurement. The well-aligned ZnO nanowalls are expected to be utilized as building blocks for field emitters and UV LEDs. The proposed technique can be used as one of the effective methods to control the growth position of the ZnO nanocrystals because various structures can be easily fabricated by a laser writing and a spatial light modulator. [ABSTRACT FROM AUTHOR]