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In this work, CuInGaSe (CIGS) thin films were prepared by nanosecond (ns)- and femtosecond (fs)-pulsed laser deposition (PLD) processes. Different film growth mechanisms were discussed in perspective of the laser-produced plasmas and crystal structures. The fs-PLD has successfully improved the inherent flaws, CuSe, and air voids ubiquitously observed in ns-PLD-derived CIGS thin films. Moreover, the prominent antireflection and excellent crystalline structures were obtained in the fs-PLD-derived CIGS thin films. The absorption spectra suggest the divergence in energy levels of radiative defects brought by the inhomogeneous distribution of elements in the fs-PLD CIGS, which has also been supported by comparing photoluminescence (PL) spectra of ns- and fs-PLD CIGS thin films at 15 K. Finally, the superior carrier transport properties in fs-PLD CIGS were confirmed by fs pump-probe spectroscopy and four-probe measurements. The present results indicate a promising way for preparing high-quality CIGS thin films via fs-PLD. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the studies on the hetero-epitaxial growth of wurtzite indium nitride (InN) thin films on oxide buffer layer by RF metal-organic molecular beam epitaxy (RF-MOMBE) system. Oxide buffer layer was pre-sputtered using RF sputtering technique. The structural properties and surface morphology were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). We also investigated the optical properties by temperature-dependence photoluminescence (PL). Near-infrared emission peak centered at 0.75eV was observed from PL measurement. The irregular and asymmetric PL line shape was caused by absorbed moisture and surface electron accumulation in InN films. According to the fitting results of PL spectra measured at 20K, we could estimate the bandgap and Fermi level is 0.65eV and 113meV, which confirm to previous reports. Our results reveal that the oxide thin film could be a suitable buffer layer for engineering the growth of InN on sapphire wafer, and it might be also applicable for other lattice-mismatched III-V hetero-epitaxial systems. [Copyright &y& Elsevier]

Abstract: In this paper, high-quality wurtzite indium nitride was epi-grown on sapphire substrates by plasma-assisted metal-organic molecule beam epitaxy system (PA-MOMBE). Structural and electrical properties of the InN films were significantly improved by employing a GaN buffer layer. In addition, high-resolution X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), Hall Effect, Raman and photoluminescence spectroscopy were carried out to characterize the effect of the growth temperature on structural and optoelectronic properties. It was found that highly c-axis oriented InN epilayer can be obtained by optimizing growth conditions. TEM images reveal that the epitaxially grown InN/GaN interface is sharp, and the spacing of the InN(0002) lattice plane is about 0.57nm. Raman spectra also show a sharp peak at 491cm−1 attributed to the E2(high) mode of wurtzite InN. These results indicate that the improvement of InN material quality can be achieved using heteroepitaxy on GaN/sapphire templates. [Copyright &y& Elsevier]

Abstract: The temperature dependence of optical properties of InGaAsN/GaAs single-quantum wells grown by solid source molecular beam epitaxy (MBE) with N contents varied from 0% to 5.3% was investigated by photoluminescence (PL). The evolution of the peak positions of InGaAs/GaAs sample are in agreement with the empirical Varshni model. However, pronounced temperature-dependent S-shaped peak positions and N-shaped linewidth were observed in PL spectra while increasing nitrogen concentration. The activation energy of InGaAsN/GaAs single quantum well (SQWs) is observed to decrease with nitrogen incorporation, which is contrary to the expectation of the bandgap reduction. This phenomenon suggests that the existence of defect-related nonradiative processes is due to nitrogen incorporation. The results of measurement demonstrate that the nitrogen incorporation into the InGaAsN has strong influence not only on carrier localization but also on the optical quality. In addition, the growth of high nitrogen content (5.3%) shows that the InGaAsN might be the potential candidate for long-wavelength optoelectronic devices. [Copyright &y& Elsevier]

Abstract: The correlation between structural and optical properties of indium nitride epilayer grown on gallium nitride/c-sapphire by radio frequency metal-organic molecular beam epitaxy is reported in this work. We discussed the effect of substrate temperature on the structural and optical properties of epitaxial indium nitride. The structural properties of the indium nitride films were characterized in detail using X-ray diffraction, field emission scanning electron microscopy and transmittance electron microscopy, and the electrical and optical properties were studied by Hall Effect and photoluminescence measurements. X-ray diffraction results indicated that indium nitride films were grown with a high degree of orientation along the c-axis, and their lattice constant is about 0.57nm. Scanning electron microscopy images show that the growth of indium nitride proceeded in two-dimensional mode and the maximum thickness is about 700nm. Our technique allowed the deposition of indium nitride at high growth rate of about 1.5μm/h. Optical measurements on the films revealed that a luminescence feature near-infrared emission peak is centered at 0.75eV. The electron concentrations of the undoped films were found to range from 1.9×1019 to 9.3×1020 cm−3 and the mobility varied from 30 to 464cm2/Vs. [Copyright &y& Elsevier]

Abstract: In this study, we discussed the effects of growth parameters on the structural and optical properties of Al-doped zinc oxide (AZO) deposited at room temperature by radio-frequency magnetron sputtering. The AZO films have been characterized in detail using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, Hall-effect measurement system and UV–visible spectrophotometer. It was found that the morphological, structural, electrical and optical properties of AZO films are greatly dependent on sputtering power. Collision between sputter species and surface morphology play important roles in optoelectrical properties of AZO films. According to our experimental results, the AZO films can be used in versatile devices to meet various requirements. [Copyright &y& Elsevier]