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In this paper an all-optical half adder has been designed on a 2D photonic crystal slab having air holes in a hexagonal lattice pattern. The working principal of the device is based on beam interference. Multi-mode interference based Pi phase shifter been used in this design. Neither any nonlinear materials nor any extra bias signal has been incorporated in the structure. Plain wave expansion and Finite Difference Time Domain methods have been used for analyzing the band diagram of the structure and performance of the proposed device respectively. The SUM port provides 60%, 67%, and 1% transmittance whereas the CARRY port provides 4%, 1%, and 90% transmission for {0,1}, {1,0}, and {1,1} logic combinations respectively. Minimum contrast ratio has been obtained as 18 dB in SUM port and 12.5 dB in CARRY port. Therefore, it is expected that the proposed all-optical adder would be a potential candidate for future generation photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Design of an all-optical 1:2 decoder has been proposed based on a holes-in-slab photonic crystal structure. Operation of the device depends on optical interferometry of an input and a bias signal. In order to achieve wavelength independent optical interference, a multimode Interference (MMI) based π-phase shifter is proposed, analysed and integrated within the design of the decoder. Dispersion diagram of the MMI π-phase shifter depicts almost equal slope of two propagation bands for a long range of wavelengths, which ensures its wavelength insensitive phase-shift operation. Finite Difference Time Domain (FDTD) simulation also confirms the same. Further, several simulations and corresponding analyses for evaluating different performances of the decoder have also been performed. These analyses exhibit the successful decoding operation of the device. The decoder performance has also been studied under the excitation of pulsating input and bias. This study concludes that the device is able to process a bit-rate as-high-as 2.94 Tbps. This small footprint (~ 243 µm2) device also offers an excellent contrast ratio of the order of 20 dB. Hence, it is expected that the device would be a potential candidate for implementing complex circuitries in photonic integrated circuits. [ABSTRACT FROM AUTHOR]

In this paper, a simple design of all-optical photonic crystal (PhC) based 1:2 line decoder has been proposed and its operating principle is based on light beam interference. The designed structure has a hexagonal arrangement of air holes in Si substrate with a finite slab height. In our proposed structure, different path lengths have been made so that the light beams should interact out of phase. Effective refractive index method has been adopted to reduce the simulation time. The Finite Difference Time Domain (FDTD) and Plane Wave Expansion (PWE) methods have been applied to evaluate the proposed structures. The required footprint area for proposed device is reported as 215 µm2. Minimum contrast ratio between the logic states of “1” and “0” is obtained as 10 dB. This device is designed based on solely linear optical phenomena in a holes-in-slab PhC structure. Therefore, mechanically stabled, ultra-compact design and simple working mechanism of the proposed optical decoder can be a potential candidate for future generation Photonic Integrated Circuits (PICs).

Interband photoluminescence was obtained for structures with multiple quantum wells (MQWs) with different content of germanium and tin. Peak position in photoluminescence spectra obtained from the MQW of Ge Si Sn /Si shifts to the long wavelength region with an increase in the Ge content in the solid solution and is observed in the energy range 0.85-0.68 eV for the germanium content from 30 to 78 . Thus, the shift of the peak along the wavelength was observed from 1.46 to 1.82 m, and the total spectral range of MQW luminescence covered by these structures was 1.3–2.1 m. An even more significant shift of the MQW photoluminescence peak to the long-wavelength region was achieved by increasing the tin content. Increasing the fraction of Sn from 7 to 14 while keeping the 30 Ge fraction constant led to a shift of the peak from 0.85 to 0.75 eV. A simultaneous increase in the content of both tin and germanium in the solid solution (up to 14 and 79%, respectively) made it possible to obtain a photoluminescence peak with an energy of 0.58 eV, which corresponds to the radiation wavelength of 2.14 m. A sharp "red" shift in the position of the photoluminescence peak with increasing temperature was discovered and its value reached 50 meV when the sample heating temperature was changed from 11 to 60–80 K. Such a significant shift in the position of the MQW photoluminescence peak is explained within the framework of a model that assumes that at low temperatures, charge carriers are randomly localized on spatial inhomogeneities of the MQW, and as the temperature increases, they are redistributed and transition to a thermodynamically equilibrium state with the lowest energy. [ABSTRACT FROM AUTHOR]

In the present work, the intrinsic nuclear structures of the 180–190W isotopes have been systematically investigated by employing the triaxial projected shell model within the deformed basis. The diagonalization of model Hamiltonian gives rise to yrast spectra, γ- and 2γ-bands which successfully describe the intrinsic band structure of these tungsten isotopes. In addition, the role of the i13/2 neutron orbitals of the intruder major shell N = 6 in explaining nuclear structure properties is also highlighted. Further, other nuclear structure properties like back-bending in moment of inertia, interband and intraband transition probabilities, wave-functions, nuclear g-factors, etc. have also been calculated and are compared with the known experimental data to get an in-depth understanding of the intrinsic nuclear structure of 180–190W isotopes. [ABSTRACT FROM AUTHOR]

TiO 2 is the most widely used material in photoelectrocatalytic systems. A key parameter to understand its efficacy in such systems is the band bending in the semiconductor layer. In this regard, knowledge on the band energetics at the semiconductor/current collector interface, especially for a nanosemiconductor electrode, is extremely vital as it will directly impact any charge transfer processes at its interface with the electrolyte. Since direct investigation of interfacial electronic features without compromising its structure is difficult, only seldom are attempts made to study the semiconductor/current collector interface specifically. This work utilizes ultraviolet photoelectron spectroscopy (UPS) to determine the valence band maximum ( E VBM ) and Fermi level ( E F ) at different depths in a nano-TiO 2 /TiN thin-film system reached using an Ar gas-clustered ion beam (GCIB). By combining UPS with GCIB depth profiling, we report an innovative approach for truly mapping the energy band structure across a nanosemiconductor/current collector interface. By coupling it with X-ray photoelectron spectroscopy (XPS), correlations among chemistry, chemical bonding, and electronic properties for the nano-TiO 2 /TiN interface could also be studied. The effects of TiO 2 in situ electrochemical reduction in aqueous electrolytes are also investigated where UPS confirmed a decrease in the semiconductor work function (WF) and an associated increase in n-type Ti 3+ centers of nano-TiO 2 electrodes post use in a 0.2 M potassium chloride solution. We report the use of UPS to precisely determine the energy band diagrams for a nano-TiO 2 /TiN thin-film interface and confirm the increase in TiO 2 n-type dopant concentrations during electrocatalysis, promoting a much more comprehensive and intuitive understanding of the TiO 2 activation mechanism by proton intercalation and therefore further optimizing the design process of efficient photocatalytic materials for solar conversion.

• CIGS layer is made thinner to lower the cost, while a second CuZnSnSe (CZTSe)-layer absorber is added to maintain high cell performance. • The new proposed cell structure designed onto a ZnO-Al film that is experimentally electrodeposited onto FTO/Glass substrate, and then characterized. • The simulation has been conducted by the TCAD SILVACO using ATLAS module. • Alternatively, 22.40 to 29.22% efficiency improvement is achievable by CZTSe addition to a thin CIGS layer. CuInGaSe (CIGS) based solar cells are promising, but involve costly and hazardous and costly indium element. This work aims at solving these problems, without sacrificing the benefits of CIGS systems. The approach is to use thinner CIGS layers. However, very thin layers minimize absorption and lower cell performance. Adding a second CuZnSnSe (CZTSe)-layer absorber should maintain high cell performance. The new proposed cell that has been simulated is MgF 2 /ZnO/Al/ZnO:i/CdS(n)/CZTSe(p)/CIGS(p)/Mo, with MgF 2 antireflection layer, ZnO:i passivating layer, CdS emitter layer, CZTSe/CIGS double absorber layer, ZnO-Al transparent conductor oxide(TCO) and element almolybdenum (Mo) back contact. A ZnO-Al film has been experimentally electrodeposited onto FTO/Glass substrate, and then characterized. TCAD SILVACO using ATLAS module has been used in the simulation. Various parameters, including layer-thickness and doping-concentration, are optimized, keeping smaller CIGS-layer thickness. Band-diagrams, carrier-concentrations and current–density, in addition to possible recombination processes, are investigated to assess performance enhancement. The results show that increasing the one-absorber CIGS-layer thickness by 2.5-fold, increases conversion efficiency from 22.3 to 24.3% only, which does not justify the extra costs. Alternatively, efficiency improves from 22.40 to 29.22% by adding CZTSe to a thin 1.0 μm CIGS layer. In conclusion, the study highlights the added value for the second-absorber layer. [ABSTRACT FROM AUTHOR]

Semiconducting heterojunctions (HJs), comprised of atomically thin transition metal dichalcogenides (TMDs), have shown great potentials in electronic and optoelectronic applications. Organic/TMD hybrid bilayers hold enhanced pumping efficiency of interfacial excitons, tunable electronic structures and optical properties, and other superior advantages to these inorganic HJs. Here, we report a direct probe of the interfacial electronic structures of a crystalline monolayer (ML) perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA)/ML-WSe2 HJ using scanning tunneling microscopy, photoluminescence, and first-principle calculations. Strong PTCDA/WSe2 interfacial interactions lead to appreciable hybridization of the WSe2 conduction band with PTCDA unoccupied states, accompanying with a significant amount of PTCDA-to-WSe2 charge transfer (by 0.06 e/PTCDA). A type-II band alignment was directly determined with a valence band offset of ∼ 1.69 eV, and an apparent conduction band offset of ∼ 1.57 eV. Moreover, we found that the local stacking geometry at the HJ interface differentiates the hybridized interfacial states. [ABSTRACT FROM AUTHOR]

Abstract Herein, metal-oxide-semiconductor fields effect transistors (MOSFET) are fabricated and characterized. p − type germanium dioxide coated onto Au/ n-CdSe substrates and top contacted with carbon point contacts is used to form the MOSFET devices. The structural investigations which were carried out with the help of X-ray diffraction technique revealed large lattice mismatched polycrystalline layers of CdSe and GeO2. The design of the energy band diagram has shown the formation of two Schottky arms (Au/ n − CdSe, C/GeO2) at the interfaces of the n − CdSe/ p − GeO2 layers. The capacitance-voltage characteristics which are recorded in the frequency domain of 1.0-50.0 MHz revealed the ability of formation of NMOS and PMOS layers. The signal frequency controlled built in potential is tunable in the range of 2.34 and 5.18 eV. In addition, the conductance and capacitance spectral analyses in the frequency domain of 10-1800 MHz revealed the domination of current conduction by tunneling and correlated barriers hoping below and above 760 MHz, respectively. In addition to its features as MOSFET devices, the Au/CdSe/GeO2/C hybrid devices are found to be appropriate for use as microwave cavities.

A new method for constructing energy band diagrams based on EPR spectroscopy data is proposed and applied to study nitrogen-doped nanocrystalline oxides of titanium, molybdenum, and vanadium (TiO2, MoO3, V2O5) with a specific surface area of about 100 m2/g and an average nanoparticle size of 10–15 nm. Nitrogen N• radicals and Ti3+ centers were detected in TiO2, N•, NO• centers and Mo5+ ions in MoO3, and V4+ centers in V2O5. The defect concentrations were 6.5 × 1017, 9.8 × 1016, and 2 × 1017 g–1, respectively. The position of the radical energy levels in the forbidden band is determined using the EPR method. The unique properties of TiO2 with a high concentration of radicals and a photocatalysis rate can be used to create energy-efficient photocatalytic devices operating in the visible range of the spectrum. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen terminated N-UNCD exhibits low capacitance and faradaic photoresponse. • Oxygen terminated N-UNCD exhibits high capacitance and capacitive photoresponse. • Unlike single-crystal diamond, both surfaces have a positive electron affinity. • Hydrogen-terminated N-UNCD possessed the lowest electron affinity at + 0.4 eV. • Differences in valence band edge positions can explain electrochemical reactivity. In recent years, various forms of nanocrystalline diamond (NCD) have emerged as an attractive group of diamond/graphite mixed-phase materials for a range of applications from electron emission sources to electrodes for neural interfacing. To tailor their properties for different uses, NCD surfaces can be terminated with various chemical functionalities, in particular hydrogen and oxygen, which shift the band edge positions and electron affinity values. While the band edge positions of chemically terminated single crystal diamond are well understood, the same is not true for nanocrystalline diamond, which has uncontrolled crystallographic surfaces with a variety of chemical states as well as graphitic grain boundary regions. In this work, the relative band edge positions of as-grown, hydrogen terminated, and oxygen terminated nitrogen-doped ultrananocrystalline diamond (N-UNCD) are determined using ultraviolet photoelectron spectroscopy (UPS), while the band bending is investigated using photoelectrochemical measurements. In contrast to the widely reported negative electrode affinity of hydrogen terminated single crystal diamond, our work demonstrates that hydrogen terminated N-UNCD exhibits a positive electron affinity owing to the increased surface and bulk defect densities. These findings elucidate the marked differences in electrochemical properties of hydrogen and oxygen terminated N-UNCD, such as the dramatic changes in electrochemical capacitance. [ABSTRACT FROM AUTHOR]

Recently it has been found that the heterostructures of n-ZnO/p-Si are promising photovoltaic alternatives to silicon homojunctions. It is well known that the energy band diagram of a heterostructure is crucial for the understanding of its operation. This paper analyzes the ZnO/p-Si heterostructure band by using free AMPS-1D computer program simulations. The obtained numerical results are compared with theoretical calculations based on the depletion region approximation model and the Poisson's equation for electric potential. The results of the simulation are also compared with the experimental C-V characteristics of the test n-ZnO/p-Si heterostructure. The simulated C-V characteristics is qualitatively consistent with the experimental C-V curve, which confirms the correctness of the determined band diagram of the n-ZnO/p-Si heterostructure. [ABSTRACT FROM AUTHOR]

Corrosion inhibitors are added in low concentrations to corrosive solutions for reducing the corrosion rate of a metallic material. Their mechanism of action is typically the blocking of free metal surface by adsorption, thus slowing down dissolution. This work uses electrochemical impedance spectroscopy to show the cyclic oligosaccharide β-cyclodextrin (β-CD) to inhibit corrosion of zinc in 0.1M chloride with an inhibition efficiency of up to 85%. Only a monomolecular adsorption layer of β-CD is present on the surface of the oxide covered metal, with Raman spectra of the interface proving the adsorption of the intact β-CD. Angular dependent X-ray photoelectron spectroscopy (ADXPS) and ultraviolet photoelectron spectroscopy (UPS) were used to extract a band-like diagram of the β-CD/ZnO interface, showing a large energy level shift at the interface, closely resembling the energy level alignment in an n–p junction. The energy level shift is too large to permit further electron transfer through the layer, inhibiting corrosion. Adsorption hence changes the defect density in the protecting ZnO layer. This mechanism of corrosion inhibition shows that affecting the defect chemistry of passivating films by molecular inhibitors maybe a viable strategy to control corrosion of metals.

This work deals with elastically strained GeSiSn films and GeSiSn islands. The kinetic diagram of GeSiSn growth for different lattice mismatches between GeSiSn and Si has been drawn. The multilayered periodic structures with pseudomorphic GeSiSn layers and GeSiSn island arrays have been obtained. The density of the islands in the GeSiSn layer is 1.8 · 1012 cm-2 for an average island size of 4 nm. Analysis of the rocking curves has shown that the structures contain smooth heterointerfaces, and no abrupt changes of composition and thickness between periods have been found. Photoluminescence has been demonstrated and calculation of band diagram with the model-solid theory has been carried out. Luminescence presented for sample with pseudomorphic Ge0.315Si0.65Sn0.035 layers in the narrow range 0.71–0.82 eV is observed with the maximum intensity near 0.78 eV corresponding to 1.59 µm wavelength. Based on the band diagram calculation for Si/Ge0.315Si0.65Sn0.035/Si heterocomposition we have concluded that 0.78 eV photon energy luminescence corresponds to interband transitions between the X-valley in Si and the heavy hole subband in the Ge0.315Si0.65Sn0.035 layer.

MOCVD grown AlGaN/GaN heterostructures on sapphire and silicon substrates have been studied. The capacity–voltage characteristic have been measured in the 200 Hz–1 MHz frequency range with a planar position of mercury and second probe on the specimen surface. The shape of the typical C–V curves for the heterostructures with upper undoped i-AlGaN and i-GaN layers 1,5–2,5 nm in thickness have been analyzed. The appearance of a typical peak on the C–V curves upon a change from the depletion region to the accumulation region has been registered in some structures with an i-GaN layer thickness of 5 nm and more at low frequencies (f

The feasibility of making Schottky barriers from Bi-nSi diode has been demonstrated. The barrier height (Ø Bn) of the Schottky contact was estimated via four creditable methods: I-V in the dark, I-V under illumination, C-V, and Fowler plot method. Such a study has been done for the first time. Barrier height ranged from 0.74 to 0.78 eV was obtained which is in disagreement with simple theory of Schottky. Rapid thermal annealing under optimum conditions leads to a decrease in the Ø Bn which is in good agreement with the expectations. Results of ideality factor for Bi-nSi revealed that the thermionic emission current is not dominant through this junction. [ABSTRACT FROM AUTHOR]

Abstract In this paper we proposed a hierarchical structure with tetrad elliptical patterns in perforated plates. It is discovered that the introduction of structural hierarchy can enhance wave energy localization and introduce additional band gaps in 3d plates, in which elastic wave cannot propagate. However, if the hierarchical level increases further, extra vibration modes will be introduced, which may lead to the narrowing or vanishing of the band gaps. Parametric studies have been carried out to illustrate the possibility of tuning band gaps with geometric variation, and the results also demonstrate that the effect of structural hierarchy is not only limited to one specific geometric configuration. In this study, the finite element analysis and band diagram analysis are used for investigation. Moreover, experimental tests have been conducted for level-1 and level-2 perforated plates for comparison, and excellent agreement between numerical analysis and experimental tests has been achieved, which also shows the feasibility of applying this strategy in structural design and other vibration mitigation applications. [ABSTRACT FROM AUTHOR]

Growth of GaN fibers by facile electrospinning method and the effect of precursor concentration on structural and optical properties have been reported. X-ray diffraction confirms the wurtzite structure of the synthesized GaN nanofibers. SEM images shows the length and diameter of the fibers increased as the precursor concentration increases. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) confirmed the crystalline nature of wurtzite GaN nanofibers. Optical properties were also investigated using diffuse reflectance spectroscopy (DRS) and photoluminescence, which shows the optical band gaps of the grown GaN nanofibers is 3.28 eV. This work confirms the precursor concentrations play a key role on the structural, morphological and optical properties of synthesized GaN nanofibers. [ABSTRACT FROM AUTHOR]

Highlights • SnO and SnO 2 epitaxial films achieved by pulsed laser ablating a metallic tin target. • The epitaxial relationships between the films and the substrates are determined. • Band diagrams of SnO and SnO 2 are determined. • p - and n-type conductivity for SnO and SnO 2 are confirmed. • Raman spectroscopy can well identify the crystal quality of SnO. Abstract Stannous oxide (SnO) and stannic oxide (SnO 2) are both important wide-band-gap semiconductors. To study the conductive mechanism in detail, high quality epitaxial films are essential. Here we propose a simple method to grow high quality epitaxial films of either stannous oxide or stannic oxide on an r -plane sapphire substrate by using pulsed laser deposition with a metallic tin target. The valence state of tin is controlled by tuning the oxygen pressure during the deposition procedure. Metal tin impurities and the transition phase of Sn 3 O 4 are avoided and the growth windows from stannous oxide to stannic oxide are confirmed. For single-crystalline SnO epitaxial film, a rocking curve half-width of 0.22° is obtained, which is better than the 0.46° of that on a YSZ substrate. The minimum roughnesses achieved were 0.37 nm for the SnO 2 epitaxial film and 0.84 nm for the SnO epitaxial film. The epitaxial relationship between SnO and the r -sapphire substrate was determined to be SnO [ 1 ¯ 1 0 ] //sapphire [ 1 ¯ 2 1 ¯ 0 ] and SnO [1 1 0]//sapphire [ 1 0 1 ¯ 1 ]. For SnO 2 , the epitaxial relation is SnO 2 [0 1 0]//sapphire [ 1 ¯ 2 1 ¯ 0 ] and SnO 2 [ 1 ¯ 0 1 ] //sapphire [ 1 0 1 ¯ 1 ]. The band schematics, deduced by combined XPS valence band spectroscopy and optical transmittance spectroscopy, indicated p -type bands of SnO and n -type bands of SnO 2. Raman spectroscopy is suggested to be a superior fingerprint of SnO single-crystalline quality, due to its greater sensitivity than X-ray diffraction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The composite of ZnO nanorods and few-layer MoS 2 was studied as a photocatalyst. • The composite has a higher absorption and a lower recombination rate than pure ZnO. • MoS 2 enhances (weakens) ZnO activity under sunlight (UV-blocked sunlight). • The observations were discussed based on band diagrams of the ZnO/MoS 2 composite. • We discussed the role of MoS 2 (ZnO) as an efficient (inefficient) e-h separator. Abstract Few-layer exfoliated MoS 2 nanosheets were easily composited with ZnO nanorods. It was found that MoS 2 nanosheets could enhance the sunlight-induced photocatalytic activity rate of ZnO by 74%. In addition, we showed that under UV-blocked sunlight irradiation, MoS 2 weakens the photocatalytic activity rate of ZnO by 33%. Finally, we discussed the mechanisms behind the enhanced (weakened) photocatalytic activity under sunlight (UV-blocked sunlight) irradiation based on the UV-Vis absorption and photoluminescence spectra as well as the potential band diagrams of the ZnO/MoS 2 composite. [ABSTRACT FROM AUTHOR]

Zinc sulphide (ZnS) thin films were deposited on glass substrate by micro‐controller‐based successive ion layer adsorption and reaction method using ZnCl2 as a precursor. The films were found to be polycrystalline. The crystallite size of the films increased with the increase in both precursor concentration and immersion cycles. The increased crystallite size resulted in the reduction of grain boundary defects which, in turn, improved the electrical properties of the films. The energy band structure of the films was analysed using absorbance and photoluminescence spectra. The films displayed strong absorption for wavelengths less than 400 nm indicating the presence of a wide bandgap with shallow defect levels near the band edges. The bandgap of the films was estimated to be between 3.3 and 3.5 eV. The photoluminescence spectra of the films exhibited a prominent excitonic peak at around 3.33 eV. The defect level emissions were observed at around 3.1, 2.92, 2.76, and 2.64 eV. These emissions were attributed to the transitions from localized zinc and sulphur vacancy levels and interstitial states. An energy band diagram of the films was drawn based on the result of optical and photoluminescence studies. [ABSTRACT FROM AUTHOR]

In this article, the physical design, energy band diagram, temperature dependent electrical resistivity and the impedance spectroscopy measurements of the Au/Bi2O3/ZnS/Ag isotype heterojunction devices are reported. The devices are prepared by the thermal evaporation technique under vacuum pressure of 10-5 mbar. Structural, compositional and morphological studies has shown the presence of an expansion in the lattice of Bi2O3 associated with increased strain and dislocation density and decreased grain size as a result of ZnS interfacing. The design of the band diagram indicated that the formed heterojunction exhibit large valence and conduction band offsets that forces charge accumulation at the interface. The Au/Bi2O3/ZnS/Ag device displays negative capacitance (NC) effect in the frequency domain of 0.01-1.50 GHz. The NC effect is interrupted by a resonance-antiresonance phenomenon in the frequency domain of 0.90-1.07 GHz. In addition to the NC effects, the device under study exhibited reflection coefficient and return loss spectra that nominate it for use as microwave cavities or as low pass band filters. [ABSTRACT FROM AUTHOR]

In the past decade, meta-materials have drawn increasing attention from researchers due to their unique properties, including wave attenuation with potential applications in acoustic engineering. A number of meta-material designs have been proposed for wave attenuation at different frequencies. In this work, a new configuration of chiral honeycomb composites is proposed for the attenuation of mid to low frequency elastic waves in structural applications. The dispersion characteristics of the proposed structure were investigated numerically. The results show that the proposed structure is able to create multiple bandgaps at mid frequency range. Interestingly, two extra bandgaps induced by local resonance effect can be created with slight reduction of the chiral angle of the structural unit cell, and one bandgap is located in the low frequency range. The wave attenuation performance of the proposed composite structure was also simulated using sound transmission loss finite element analysis, demonstrating its potential in real applications. [ABSTRACT FROM AUTHOR]

A novel-gated structure of aluminum (Al)—perovskite (CH3NH3PbI3)—indium tin oxide (ITO), with Al as source and ITO as drain terminals, has been reported. Ambipolar nature of CH3NH3PbI3 has been explored for the device channel. Two Schottky junctions are present at source–channel and channel–drain junctions with barriers of 0.4 and 0.6 eV, respectively. Both, n- and p-type FET-like characteristics have been observed, when the device was biased, accordingly. The triangular tunneling has been observed in the output and transfer characteristics. The device shows a higher current on-off ratio ( ${I}_{ \mathrm{\scriptscriptstyle ON}}/_{ \mathrm{\scriptscriptstyle OFF}})$ of 106 with a steeper and improved sub-threshold swing (SS) of 20 ± 2 mV/decade for P tunnel field-effect transistor (TFET). However, for N TFET, ${I}_{ \mathrm{\scriptscriptstyle ON}}/_{ \mathrm{\scriptscriptstyle OFF}}$ of 104 with SS of 30 ± 2 mV/decade has been obtained. [ABSTRACT FROM AUTHOR]

Development of ultra-sensitive and selective 2-propanol sensor employing hybrid structure of reduced graphene oxide (rGO) and 3-D ZnO nanoflowers (NFs) is reported in this paper. The 3-D ZnO NFs were synthesized on n-Si wafer, using liquid phase deposition technique, while a dip coating technique was adopted for the deposition of rGO, in the form of discrete claddings, on the ZnO NFs layer. The detailed morphological (field emission scanning electron microscopy) and structural (Raman and XPS) characterizations were carried out to compare the structural and morphological properties of pristine ZnO NFs and rGO-ZnO NFs hybrid structure. The sensing properties of ZnO NFs and rGO-ZnO NFs devices were investigated toward different alcohol vapors (2-propanol, ethanol, and methanol) in the concentration range of 0.5–700 ppm at 100 °C–275 °C. The rGO-ZnO NFs 3-D hybrid device offered ultra-high sensitivity (645% response magnitude at 700 ppm) toward 2-propanol at ~160 °C. In addition, the same sensor also offered excellent selectivity against interfering neighbors (i.e., ethanol, methanol, acetone, and benzene). The underlying mechanism for such experimental findings has been discussed with the properties of rGO–ZnO hybrid junction and respective band bending in air and target species. [ABSTRACT FROM PUBLISHER]