Optimization of Zr-doped ZnO thin films prepared by sol-gel method

Semiconductor thin films of Zr-doped ZnO, with Zr concentrations varying from 0 to 5 at%, have been prepared using a sol-gel method. Crystallinity, microstructure, and optical properties affected by Zr concentration were investigated. In this study, Zr-doped ZnO thin films were deposited onto alkali-free glass substrates by spin-coating. The as-deposited films were preheated at 300 C and then annealed at 500 C in air. The experimental results showed that doping ZnO thin films with Zr not only refined the grain size but also increased transmittance and resistivity. Among all the thin films investigated in the present study, the 3 at% Zr-doped ZnO thin film exhibited the best properties with a transmittance of 86.3% and a RMS roughness value of 5.86 nm. In addition, thin-film transistors were fabricated by spin-coating a 3 at% Zrdoped ZnO active channel layer onto a transistor subassembly. These transistors exhibited n-type depletion mode in which threshold voltage and drain current on-to-off ratio were À18:0 V and 9:6 Â 10 5 , respectively

Properties of Transparent Yttrium Oxide Dielectric Films Prepared by sol–gel Process

[[abstract]]In this research, yttrium oxide (Y2O3) gate dielectric films were deposited onto alkali-free glass substrates by a sol–gel process. This report describes the effects of annealing temperatures on the microstructural and electrical properties of sol–gel derived Y2O3 films. These sol–gel films were preheated at 300 °C for 10 min, and then annealed at 400–550 °C for 1 h. XRD results revealed that all annealed films exhibited preferential (2 2 2) orientation; films annealed at 450–550 °C were polycrystalline with cubic structures. The average transmittances of polycrystalline Y2O3 films were over 88.0% in the visible range. The electrical properties of the Y2O3 films were analyzed by capacitance–voltage (C–V) and current–voltage (I–V) measurements. Films annealed at 500 °C yielded the lowest leakage current density, 1.8 × 10−7 A/cm2, at an applied voltage of 5 V, and had a dielectric constant of 10.0 at 100 kHz

Comparative Studies on Ultraviolet-Light-Derived Photoresponse Properties of ZnO, AZO, and GZO Transparent Semiconductor Thin Films

ZnO, Al-doped ZnO (AZO), and Ga-doped ZnO (GZO) semiconductor thin films were deposited on glass substrates via a sol-gel spin-coating process for application in a photoconductive ultraviolet (UV) detector. The doping concentrations of Al and Ga were 1.0 at % in the precursor solutions. In this study, the microstructural features and the optical and electrical properties of sol-gel-derived ZnO, AZO, and GZO thin films were compared, and the performance of ZnO-based UV photodetectors under ultraviolet A (UVA) light were measured. Experimental results confirmed the synthesis of single-phase nanocrystalline ZnO-based thin films and the successful substitution of Al and Ga into Zn sites in ZnO crystals. The results also demonstrated that the optical transmittance and electrical properties of ZnO thin films could be improved by Al and Ga doping. UV photodetectors based on ZnO-based thin films, having a metal-semiconductor-metal (MSM) configuration, were fabricated with Al inter-digitated electrodes. All photodetectors showed an ohmic nature between semiconductor and electrode contacts and exhibited a sharp increase in photocurrent under illumination with UVA light. We found that the MSM UV photodetector based on the GZO semiconductor thin film exhibited the best UV response (IUVA/Idark) of 73.3 and the highest photocurrent responsivity of 46.2 A/W under UVA light (power density ~0.825 mW/cm2) at 5 V bias

Enhanced Electrical Properties and Stability of P-Type Conduction in ZnO Transparent Semiconductor Thin Films by Co-Doping Ga and N

P-type ZnO transparent semiconductor thin films were prepared on glass substrates by the sol-gel spin-coating process with N doping and Ga–N co-doping. Comparative studies of the microstructural features, optical properties, and electrical characteristics of ZnO, N-doped ZnO (ZnO:N), and Ga–N co-doped ZnO (ZnO:Ga–N) thin films are reported in this paper. Each as-coated sol-gel film was preheated at 300 °C for 10 min in air and then annealed at 500 °C for 1 h in oxygen ambient. X-ray diffraction (XRD) examination confirmed that these ZnO-based thin films had a polycrystalline nature and an entirely wurtzite structure. The incorporation of N and Ga–N into ZnO thin films obviously refined the microstructures, reduced surface roughness, and enhanced the transparency in the visible range. X-ray photoelectron spectroscopy (XPS) analysis confirmed the incorporation of N and Ga–N into the ZnO:N and ZnO:Ga–N thin films, respectively. The room temperature PL spectra exhibited a prominent peak and a broad band, which corresponded to the near-band edge emission and deep-level emission. Hall measurement revealed that the ZnO semiconductor thin films were converted from n-type to p-type after incorporation of N into ZnO nanocrystals, and they had a mean hole concentration of 1.83 × 1015 cm−3 and a mean resistivity of 385.4 Ω·cm. In addition, the Ga–N co-doped ZnO thin film showed good p-type conductivity with a hole concentration approaching 4.0 × 1017 cm−3 and a low resistivity of 5.09 Ω·cm. The Ga–N co-doped thin films showed relatively stable p-type conduction (>three weeks) compared with the N-doped thin films

Hydrothermally Synthesized Mg-Based Spinel Nanoferrites: Phase Formation and Study on Magnetic Features and Microwave Characteristics

Three kinds of magnesium-based spinel nanoferrites with the chemical formulas of MgFe2O4 (Mg ferrite), Mg0.9Mn0.1Fe2O4 (Mg-Mn ferrite), and Mg0.9Mn0.1In0.1Fe1.9O4 (Mg-Mn-In ferrite) were synthesized by hydrothermal route. We report the composition-dependent magnetic parameters and microwave properties of Mg-based ferrite nanoparticles. XRD results revealed that the Mg-based ferrite nanoparticles exhibited a cubic spinel structure and had an average nanocrystallite size in the range of 5.8⁻2.6 nm. Raman spectroscopy analysis confirmed the formation of cubic-spinel phase Mg-based nanoferrites. The room-temperature magnetization measurements indicated that the Mg ferrite nanoparticles had superparamagnetic behavior; whereas the Mg-Mn and Mg-Mn-In ferrite nanoparticles exhibited a paramagnetic nature. The microwave properties of obtained ferrite nanoparticles were studied by alternating current (AC) magnetic susceptibility measurement and electron paramagnetic resonance (EPR) spectroscopy. It was found that the un-substituted Mg ferrite sample exhibited microwave characteristics better than those of the Mn substituted and Mn-In co-substituted Mg ferrite samples