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We investigated the structural and optical properties of nanoparticle-assisted pulsed laser-deposited ZnO microrods and Au-coated ZnO microrods grown on Si substrate. Our present study indicates that Au-coated ZnO microrods exhibit whispering gallery modes (WGM) in the near band edge region with significant splitting into two branches. Moreover, the WGMs exhibited blue shift with decrease in rod size. We found that the modes are well split in Au coated ZnO rods when compared with as-grown rods, resulted from the plasmon enhancement of WGM modes. We also found that the Au-coated ZnO was stable in the ambient when compared with uncoated ZnO. WGM resonance from the exciton related emission, the enhancement in WGMs, and stability in the ambient condition of the Au-coated ZnO microrods suggest great potential for small-volume devices and microlasers.

We report on the fabrication of ZnO and Zn0.9Mg0.1O microrods using nanoparticle assisted pulsed laser deposition (NAPLD). Micro-photoluminescence studies reveal that Zn0.9Mg0.1O microrods exhibited a blue shift in the ultraviolet (UV) emission relative to unintentionally doped ZnO that was attributed to the increase in bandgap due to Mg doping. High-resolution micro-photoluminescence clearly indicated the presence of whispering gallery modes (WGMs) for both ZnO and Zn0.9Mg0.1O. Transverse electric (TE) and transverse magnetic (TM) optical WGMs were identified using the existing plane-wave model. The observation of lower order WGM modes in Zn0.9Mg0.1O microrods may be of great interest for future UV WGM lasing.

KBiFe2O5 (KBFO) is an upcoming promising brownmillerite-structured multiferroic photoactive material for next-generation photovoltaic and photocatalytic applications. In the present work, KBFO has ...

In this study, the effect of annealing ambient on SnO 2 thin film transistors (TFTs) is presented. Phase pure SnO 2 films have been deposited using solution processed spin coating technique with SnCl 2 as the precursor material. The films are annealed at 500 °C for 1 h in different annealing ambient conditions with varying N 2 :O 2 ratio. Top gate, bottom contact TFTs have been fabricated with SnO 2 as the channel layer, silicon as the gate, silicon dioxide as the dielectric and gold as the contact material. XRD patterns reveal the amorphous nature of films. AFM image shows that the spin coated films are pin-hole free with extremely smooth surface morphology. PL and XPS measurements reveal that with increase in N 2 % during annealing, the defects in the films increase. However, with increase in nitrogen concentration, the device performance improves, the threshold voltage shifts towards lower values and mobility increases, but very high N 2 % is not suitable for device operation, a 70% N 2 + 30% O 2 annealing ambient is found to be suitable with devices showing saturation mobility of 0.23 cm 2 V −1 s −1 and threshold voltage of 6.8 V and on/off ratio of 10 6 .

We report on the growth of ZnO nanostructures in different gas ambient (Ar and N 2 ) using pulsed laser deposition technique. Despite the similar growth temperature, use of N 2 ambient gas resulted in well-aligned nanorods with flat surface at the tip, whereas, nanorods grown with Ar ambient exhibited tapered tips. The Nanorods grown under N 2 ambient exhibited additional Raman modes corresponding to N induced zinc interstitials. The nanorods are c-axis oriented and highly epitaxial in nature. Photoluminescence spectroscopy reveals that the UV emission can be significantly enhanced by 10 times for the nanorods grown under Ar ambient. The enhanced UV emission is attributed to the reduction in polarization electric field along the c-axis. n -ZnO nanorods/p-Si heterojunction showed rectifying I–V characteristics with a turn of voltage of 3.4 V.

We demonstrate reversible p -type nature of pulsed laser deposited (P, N) codoped ZnO thin films using rapid thermal annealing process. As grown thin films exhibited change in conductivity from p to n -type over a span of 120 days. Non-annealed n -type thin films contain unintentional donor impurities such as hydrogen and carbon. X-ray photoelectron spectroscopy and Raman measurements conclusively show that hydrogen passivates nitrogen acceptors by forming N H complex. Carbon can be annealed out at 600 °C, whereas, the dissociation of N H complex takes place at 800 °C. The films revert its p -type nature at an annealing temperature of 800 °C.

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Al2O3 was deposited on n-type 4H-SiC by reactive-ion-sputtering (RIS) at room temperature using aluminum target and oxygen as a reactant gas. Post deposition oxygen annealing was carried out at a temperature of 1100 °C. Metal-oxide-semiconductor (MOS) test structures were fabricated on 4H-SiC using RIS-Al2O3 as gate dielectric. The C-V characteristics reveal a significant reduction in flat band voltage for oxygen annealed RIS-Al2O3 samples (Vfb = 1.95 V) compared to as-deposited Al2O3 samples (Vfb > 10 V), suggesting a reduction in negative oxide charge after oxygen annealing. Oxygen annealed RIS-Al2O3 samples also showed significant improvement in I-V characteristics compared to as-deposited RIS-Al2O3 samples. A systematic analysis was carried out to investigate the leakage current mechanisms present in oxygen annealed RIS-Al2O3 on 4H-SiC at higher gate electric field and at different operating temperature. For measurement temperature (T)

Formation of ordered defect compounds and anomalous grain boundary physics are unique to Cu chalcogenides CuInX 2 (S/Se) and its alloys. X-ray photoelectron spectroscopy (XPS) studies were carried on Cu 2-x Zn 1.3 SnS 4 (x = 0.0, 0.3, 0.5 and 0.7) to determine the position of valence band edge and explore the formation of ordered vacancy compounds along with absorption studies. Conductive atomic force microscopy (C-AFM) studies were carried out Cu 2 ZnSnS 4 (CZTS) film deposited on Si and sodalime glass substrates to understand grain boundary physics.

In this paper we report the detailed analysis of the effect of in-situ annealing on the electrical properties of yttrium stabilized zirconium oxide (YSZ) thin films grown by pulsed laser deposition on silicon substrates. The optimized metal/YSZ/Si devices showed low leakage current, good dielectric strength and a breakdown field strength of 4.13 MV/cm. The magnitudes of flat band voltage, and interfacial charge density have been extracted from the capacitance-voltage (C-V) characteristics of the MOS structure. The C-V characteristics show a small hysteresis which indicates the presence of traps. The observed shift in the flat band voltage and hysteresis are explained with the help of X-ray photoelectron spectroscopy. From the XPS depth profile analysis of the samples it was found that as we go from the surface to the interface, oxygen concentration in the deposited film decreases, i.e. the oxide becomes zirconium rich. This has been correlated with the observed electrical properties.

Enhancing luminescence characteristics is one of the key challenges in ZnO nanostructures for highly efficient UV-blue LEDs and laser diodes. Non-conventional PLD growth parameters have been used to tailor the polar and semi-polar surfaces of ZnO nanostructures on MgO substrates. Despite the similar growth temperature, use of N2 ambient gas allowed the fabrication of well-aligned polar nanostructures; whereas, nanostructures grown with Ar ambient are semi-polar in nature. By means of cathodoluminescence spectroscopy, we demonstrate that the UV emission can be significantly enhanced by 11 times for semi-polar nanostructures. The enhanced luminescence is attributed to reduced polarization electric fields along the c-axis.

We report on the growth of violet emitting p-type ZnO thin films, with phosphorous (P) and nitrogen (N) codoping, using pulsed laser deposition. XPS studies show that the phosphorous is substituted at Zn site, whereas nitrogen is substituted at oxygen site. Hall measurements confirmed the p-type nature in codoped ZnO thin films. I-V characteristics of the heterojunction formed by n-Si and P, N: ZnO showed rectifying nature. Strong violet emission in PL spectra is attributed to the formation of zinc vacancies. We propose a defect complex, (PZn-VZn-4NO), which acts as an effective acceptor in the P and N codoped ZnO. � 2015 Elsevier B.V.

We report on the growth of ZnO nanowires on a p-type diamond substrate using nanoparticle-assisted pulsed laser deposition technique. Microstructural analysis on different growth stages reveals that the self-assembled 1D ZnO nanowires emerge on well-formed 2D hexagonal base with spiral-like structures. We explain the formation of screw-dislocation-driven spiral-like-hexagons invoking crystal growth velocities at different regions of the hexagons. High-resolution transmission electron microscopy and selective area electron diffraction studies show that the nanowires are single crystalline in nature and grow along 0 0 0 1 direction of the wurtzite hexagonal structure. Room temperature photoluminescence spectrum of the ZnO nanowire shows a strong near band edge emission at 3.2 eV with a linewidth of 136 meV. � 2014 IOP Publishing Ltd.