CdZnTe has been characterized by means of polarization-field hysteresis and current–voltage measurements. The CdZnTe is shown to be ferroelectric with polarization endurance up to 107 poling cycles. The polarization is significantly influenced by free carriers and can be switched by light illumination. The capacitance of CdZnTe consists of ferroelectric and depletion components. On the other hand, electrical conduction in the CdZnTe is modulated by the polarization, leading to hysteresis in the current–voltage characteristics. Writing and reading measurement has shown a reading-current difference of 0.015 mA at a nondestructive voltage for the binary digits.

The effect of surface passivation of undoped p-CdTe(100) by (NH4)2Sx treatment was investigated by using photoluminescence (PL), photoconductivity (PC), and x-ray photoelectron spectroscopy (XPS). After sulfur treatment for 2 min, the acceptor bound exciton (A0, X) peak increases greatly in the PL spectrum, and the minority-carrier lifetime of CdTe becomes the longest value in the PC measurement. The XPS spectrum for untreated CdTe shows the additional peaks on the right side of two main Te peaks corresponding to the Te 3d core levels, and these additional peaks are related to TeO3 with binding energies of 576.2 and 586.5 eV. After sulfur treatment, while the intensities of the Te 3d core levels decreased gradually, those of the TeO3 peaks disappear. In addition, the S 2p core-level spectra for sulfur-treated CdTe show the peaks at the 161.7 and 162.8 eV, which are attributed to a CdS formation at the surface of CdTe. These results indicate the sulfur effectively dissociates the native oxides from and neutralizes the dangling bonds at the surface of CdTe.

Etching of materials on the nanoscale is a challenging but necessary process in nanomaterials science. Gas sensing using a single ZnO nanocactus (NC), which was prepared by facile isotropic nanoetching of zinc oxide nanorods (NR) grown by chemical vapor deposition (CVD) using an organic photoresist (PR) by a thermochemical reaction, is reported in this work. PR consists of carboxylic acid groups (COOH) and cyclopentanone (C5H8O), which can react with zinc and oxygen atoms, respectively, on the surface of a ZnO NR. The thermochemical reaction is controllable by varying the concentration of PR and reaction time. A gas sensor was fabricated using a single NC. Gas sensing was tested using different gases such as CH4, NH3 and carbon monoxide (CO). It was estimated that the surface area of a ZnO NC in the case of 50% PR was found to increase four-fold. When compared with a single ZnO NR gas sensor, the sensitivity of a ZnO NC was found to increase four-fold. This increase in sensitivity is attributed to the increase in surface area of the ZnO NC. The formed single ZnO NC gas sensor has good stability, response and recovery time.

We report on impurity ferroelectricity and ferromagnetic properties in semiconductor-structured CdMnS films. We observed ferroelectric hysteresis in CdMnS. A remnant polarization of 1.72 μC/cm2 and a coercive field of 14.3 kV/cm were obtained in samples with Mn concentration below 2%. The coevaporated CdMnS samples become ferromagnetic when doped with Au, with a spontaneous magnetization of 1.39×10−6 emu and a coercive magnetic field of 75.4 gauss at 10 K, and the Curie point was found to be higher than room temperature. Through magnetic force microscopy, we observed clear magnetic clusters with sizes ranging from a few nanometers to 102 nm, and found the magnetization to be highly dependent on Au concentration. A combination of this ferroelectricity in CdMnS and ferromagnetism in Au-doped CdMnS may find use in ternary bit nonvolatile memory devices.

Herein, we report the self-aligned growth of GaN nanorods on different orientations of sapphire like c-, a-, rand m-plane substrates by hydride vapor phase epitaxy. Vertical c-axis orientation of GaN NRs is obtained on c-plane [0001] and a-plane 11 20 ½ sapphire and a skew or inclined NRs on r-plane, and inclined intertwined but self-aligned NR array was formed on m-plane sapphire. GaN (002) and (004) peaks were obtained on c-and a-plane sapphire, whereas (110), (103), and (103) only were observed on r-and mplanes, respectively. In the case of r-and m-plane-grown GaN, A 1 transverse optical mode is dominant, and the A 1 longitudinal optical mode is suppressed. Conversely, in the case of c-and a-plane, it is reversed. The probable reason is the optical mode vibrations difference along the differently inclined NRs surfaces. In addition, the specimen exhibits surface optical modes too. The optical behavior of GaN NR on m-sapphire shows an intensity variation when measured in different angular rotations of the specimen by photoluminescence which is because of the higher area of excitation in the case of axial surfaces and lower area of excitation in radial surface. Their epitaxial crystallographic relationship with the substrates and the reasons for the self-aligned orientations are discussed. The anomalies found in the optical behavior are attributed to Raman antenna effect and so on. The self-aligned intertwined GaN NRs find suitable applications in polarizer.