Metallic Cr film coatings of 1.2 µm thickness were prepared by DC magnetron sputter deposition method on cplane sapphire substrates. The thin Cr films were ammoniated during horizontal furnace thermal annealing for 10-240 min in NH 3 gas flow conditions between 400 and 900 o C. After annealing, changes in the crystal phase and chemical constituents of the films were characterized using X-ray diffraction (XRD) and energy dispersive X-ray photoelectron spectroscopy (XPS) surface analysis. Nitridation of the metallic Cr films begins at 500 o C and with further increases in annealing temperature not only chromium nitrides (Cr 2 N and CrN) but also chromium oxide (Cr 2 O 3 ) was detected. The oxygen in the films originated from contamination during the film formation. With further increase of temperature above 800 o C, the nitrogen species were sufficiently supplied to the film's surface and transformed to the single-phase of CrN. However, the CrN phase was only available in a very small process window owing to the oxygen contamination during the sputter deposition. From the XPS analysis, the atomic concentration of oxygen in the as-deposited film was about 40 at% and decreased to the value of 15 at% with increase in annealing temperature up to 900 o C, while the nitrogen concentration was increased to 42 at%.
ZnO thin films were grown on a sapphire substrate by RF magnetron sputtering. The characteristics of the thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL), and Hall effect. The substrate temperature and growth time were kept constant at 200 o C at 30 minutes, respectively. The RF power was varied within the range of 200 to 500 W. ZnO thin films on sapphire substrate were grown with a preferred C-axis orientation along the (0002) plan; X-ray diffraction peak shifted to low angles and PL emission peak was red-shifted with increasing RF power. In addition, the electrical characteristics of the carrier density and mobility decreased and the resistivity increased. In the electrical and optical properties of ZnO thin films under variation of RF power, the crystallinity improved and the roughness increased with increasing RF power due to decreased oxygen vacancies and the presence of excess zinc above the optimal range of RF power. Consequently, the crystallinity of the ZnO thin films grown on sapphire substrate was improved with RF sputtering power; however, excess Zn resulted because of the structural, electrical, and optical properties of the ZnO thin films. Thus, excess RF power will act as a factor that degrades the device characteristics.Key words ZnO, RF magnetron sputter, hall, PL. 서 론
In this study, GaN powders were synthesized from gallium oxide-hydroxide (GaOOH) through an ammonification process in an NH 3 flow with the variation of B 2 O 3 additives within a temperature range of 300-1050 o C. The additive effect of B 2 O 3 on the hexagonal phase GaN powder synthesis route was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transformation infrared transmission (FTIR) spectroscopy. With increasing the mol% of B 2 O 3 additive in the GaOOH precursor powder, the transition temperature and the activation energy for GaN powder formation increased while the GaN synthesis limit-time (t c ) shortened. The XPS results showed that Boron compounds of B 2 O 3 and BN coexisted in the synthesized GaN powders. From the FTIR spectra, we were able to confirm that the GaN powder consisted of an amorphous or cubic phase B 2 O 3 due to bond formation between B and O and the amorphous phase BN due to B-N bonds. The GaN powder synthesized from GaOOH and B 2 O 3 mixed powder by an ammonification route through β-Ga 2 O 3 intermediate state. During the ammonification process, boron compounds of B 2 O 3 and BN coated β-Ga 2 O 3 and GaN particles limited further nitridation processes.
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