Mahaveer Kumar Jain

Indium-rich InxGa1-xN thin films were prepared on glass substrates by a mixed source modified activated reactive evaporation technique. All the films exhibit hexagonal wurtzite structure preferentially oriented along the c-axis. The band gap values obtained through Urbach fitting of the absorption edge were found to be in good agreement with the values obtained from photoluminescence spectra. The decrease in band gap below 1.9 eV (i.e., for pure InN) for indium-rich films is mainly due to the compensation of BursteinMoss shift due to gallium incorporation into the lattice which is further confirmed from the carrier concentration measurements. © 2011 World Scientific Publishing Company.

Copper nitride thin films have been prepared by pulsed direct current reactive magnetron sputtering. Structural, morphological and optical properties of the as-deposited films have been studied. X-ray diffraction analysis shows that the films are polycrystalline single phase of Cu3N. Prominent growth along (100) plane is observed for higher nitrogen flow rate whereas growth along (111) plane is observed for relatively lower nitrogen flow rate. The band gap of this material changes from 1.02 to 1.40 eV by varying the nitrogen flow rate and deposition time. © 2013 IEEE.

Zn 1-x Cd x O thin films have been prepared by sol-gel spin coating method. Structural analysis shows that the Cd substitution into the wutrzite ZnO lattice is achieved up to about 20 mol %. The optical band gap is found to decrease with the increase in Cd content. Increase in the annealing temperature up to a certain critical temperature leads to band gap narrowing because of the proper substitution of Zn by Cd and thereafter the band gap increases due to Cd re-evaporation from the lattice sites. This critical temperature lowers down with the increase in Cd doping concentration. The resistivity decreases with the increase in Cd content and increases with the increase in annealing temperature.

Polycrystalline In x Ga 1-x N thin films were prepared by mixed source modified activated reactive evaporation (MARE) technique. The films were deposited at room temperature on glass substrates without any buffer layer. All the films crystallize in the hexagonal wurtzite structure. The indium concentration calculated from XRD peak shift using Vegard's law was found to be varying from 2% to 92%. The band gap varies from 1.72 eV to 3.2 eV for different indium compositions. The indium rich films have higher refractive indices as compared to the gallium rich films. The near infra-red absorption decreases with gallium incorporation into InN lattice which is mainly due to decrease in the free carrier concentration in the alloy system. This fact is further supported from Hall effect measurements. MARE turns out to be a promising technique to grow In x Ga 1-x N films over the entire composition range at room temperature. © 2011 Elsevier B.V. All rights reserved.

Polycrystalline MgxZn1-xO (MZO) thin films on glass substrates were prepared by sol-gel method. All the films retained the hexagonal wurtzite structure of ZnO. The band gap values determined from transmission spectra were found to be smaller than the values obtained from Vegard's law for the as-deposited MZO films. For the films with x = 0.1, 0.2 and 0.3, the band gap blue-shifted initially and then red-shifted with increase in the annealing temperature. The reason for this anomalous shift in the band gap is attributed to the proper substitution of Mg atoms into the Zn lattice sites after a certain critical annealing temperature. © Springer Science+Business Media, LLC 2009.

In this report, we have studied the compositional dependence of structural, optical and electrical properties of polycrystalline In x Ga 1-x N thin films grown by modified activated reactive evaporation. The growth was monitored by optical emission spectroscopy. The thickness of the films was in the range ∼600-800 nm. The phase, crystallinity and composition of the films were determined by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The surface morphology was studied by atomic force microscopy. The band gaps of these films obtained from transmittance and photoluminescence measurements were found to vary from 1.88 to 3.22 eV. All the films show n-type conductivity. The carrier concentration was found to be decreasing with increase in gallium incorporation which is in good agreement with the free carrier absorption observed in transmittance spectra. © 2012 Springer Science+Business Media, LLC.

Nano-crystalline c-axis orientated indium nitride (InN) thin films were prepared on amorphous polycarbonate, polyimide and glass substrates by modified activated reactive evaporation (MARE) method without any intentional heating of the substrate. The films show strong visible photoluminescence (PL) peak at ~ 1.95 eV indicating the band edge transition which is in good agreement with the optical absorption. The shift in the band gap from reported value is mainly due to Burstein-Moss shift and presence of residual oxygen. InN film grown on inexpensive flexible substrates at room temperature opens opportunity for large scale device applications like solar cells and displays. © 2009 American Institute of Physics.

Highly crystalline copper nitride (Cu3N) thin films have been deposited on glass substrates at room temperature by a novel and commercially viable growth technique, known as modified activated reactive evaporation (MARE). The effects of change in radio frequency (RF) power and deposition pressure on the structural and optical properties of the films have been investigated. RF power plays a significant role for the preferential growth of these films along a particular plane whereas the deposition pressure has comparatively lesser impact on the same. However, the lattice parameter, film thickness and optical band gap are found to be strongly dependent on the deposition pressure. The MARE grown Cu3N films undergo complete decomposition into metallic Cu upon vacuum annealing at 400 °C which makes them promising candidates to be used in write once optical recording media.

Nano-crystalline c-axis oriented In xGa 1-xN (x=0.93, 0.63, 0.5, 0.36 and 0.18) thin films were prepared by modified activated reactive evaporation technique. Phase segregation was clearly observed for x=0.5 composition. Scanning electron microscopy images reveal the average grain size for all the films to be varying from 40 to 85nm. From, the absorption spectra the band gaps for the InGaN films were found to be varying from 1.89 to 2.92eV. Micro-Raman scattering at two different excitation energies (1.96 and 2.54eV) were used to study the phase separation and compositional fluctuations of InGaN layers across their thickness. All the spectra exhibit the characteristic A 1(LO) and E 2 (high) modes corresponding to hexagonal wurtzite structure for both the excitations. No appreciable change in the peak positions for the two excitations confirms the absence of any significant phase separation across the thickness of InGaN films with x=0.36 and 0.18 composition. However, for x=0.93 and 0.63 films, gallium rich minority phase could be detected with 1.96eV excitation. The changes in the area and FWHM of the two characteristic Raman peaks for different excitations are attributed to the increased structural defects across the sample depth and also to the near resonance effects. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We report the role of charged species (N2+) on the growth of GaN films by modified activated reactive evaporation (MARE). In MARE technique, substrate is subjected to low energy nitrogen ion bombardment by keeping it in conjunction with the radio frequency cathode. The low energy ion irradiation contributes to the effective formation of GaN as well as in the drastic reduction of the oxygen impurity content by resputtering of the weakly bonded oxygen adatoms. Significant reduction in oxygen impurity can be achieved in the MARE by increasing the concentration of the charged species in the plasma. © 2010 The Electrochemical Society.