Search

In this work, CuInS 2 (CIS) nanocrystals are successfully synthesized by microwave-assisted technique and further calcined at several different temperatures with or without additional Ar ambient. The XRD measurements showed that a significant recrystallization might have occurred with the help of Ar ambient to introduce the increasing relative intensity of the (112) diffraction peak. Furthermore, the eliminated organic-related structures and the enlarging CuInS 2 nanocrystals are evidently confirmed by FTIR and SEM, respectively. Raman analysis of the CIS(CH) mode of the CuInS 2 nanocrystals in the calcined temperature range of 200–400 °C is presented while the lineshape is described and calculated by the spatial correlation model corresponding to the presence of a long-range order in the higher calcined temperature of CuInS 2 nanocrystals. Transmission can be used to figure out that the calcined CuInS 2 nanocrystals with Ar are related with the modification of the optical band gap energy.

We report the characteristics of reflectance spectra of the 15- and 20-period ZnTe/ZnSe distributed Bragg reflector grown on GaAs (001) substrates by molecular beam epitaxy. The reflectance spectra measured at various incident angles and polarizations were investigated by the theoretical curves simulated using transfer matrix method. The wavelength variation of the refractive indices described by Sellmeier equation and random thickness model were also considered for the interpretation of the experimentally observed curves. An omnidirectional reflection range defined from the edge of incident-angle-dependent reflection band with TE and TM polarizations is about 15 nm, and is consistent with the observed experimental curves. The results showed that the selected ZnTe and ZnSe materials are suitable for constructing multilayer structures having omnidirectional reflection band.

Samples containing thin InAlGaN layers grown on c -Al 2 O 3 substrates by metalorganic chemical vapor deposition have been studied experimentally and theoretically with the help of photoluminescence measurements between 10 and 300 K. From the analysis of the temperature dependence photoluminescence spectra with the modified Bose–Einstein equation, the localization energy of excitons was estimated successfully and the value is found out to be well correlated to the strength of the electron/exciton-phonon interaction as well as the stress observed in the X-ray diffraction spectra. These results are also confirmed that the c -axis length decreases as the increasing Al/In ratio corresponding to the decreased compressive stress which would be attributed to the increased tensile stress formed by Al atoms incorporated.

Photoluminescence (PL) spectra of a quaternary alloy In 0.014 Al 0.105 Ga 0.881 N thin film grown by low pressure metalorganic chemical vapor deposition (MOCVD) are studied experimentally in the temperature range of 10–300 K. It is shown that the temperature dependence can be well studied by the Eliseev's model to characterize the scale of the exciton-localization effects for the exciton localization energy. Moreover, the Urbach energy was determined from an analysis of the low-energy side of the PL lineshape. From the temperature dependence of Urbach energy, the value of Urbach energy can be described by the Einstein oscillator model which takes into consideration the contributions from both the thermal and structural disorders.

Single crystals of 2H-MoSe 2 were investigated by the anisotropic photoconductivity (PC) measurements as a function of temperature in the range of 12–300 K. A significant shift towards lower energy has been observed in the PC spectra of the edge plane with respect to the van der Waals plane. The anisotropy in the indirect energy gap is being attributed to crystal anisotropy. The parameters that describe the temperature dependence of the anisotropic indirect energy gap are evaluated and discussed utilizing the Varshni and Manoogian–Woolley semi-empirical relationships. The Debye temperature of the sample has also been estimated by the fitted values.