Radio Frequency Reactive Co-sputtering Research Articles

A study on structural formation and optical properties of Zn1-xCdxO thin films synthesized by the DC and RF reactive magnetron co-sputtering

The Zn1-xCdxO thin films were prepared on quartz by the direct current (DC) and radio frequency (RF) reactive magnetron co-sputtering technique with Zn and Cd metal targets. The influence of RF power on Cd target (PCd) on the structure and optical properties of Zn1-xCdxO films was investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM), optical absorbance and photoluminescence (PL) measurements. The concentration and chemical states of Cd in films have been confirmed by energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. The results indicated that as the PCd varied from 0 to 120 W, all the Zn1-xCdxO thin films had a hexagonal wurtzite structure of pure ZnO and highly (002) preferred orientation, the Cd relative content in film is increased and the Zn relative content is decreased. Correspondingly, the optical band-gap of Zn1-xCdxO thin films with hexagonal wurtzite structure are tuned from 3.24 (PCd = 0) to 2.82 eV (PCd = 120 W). The location of the near-band-edge (NBE) emission peaks shift toward lower energy side from 388 to 440 nm, which is attributed to the decrease of band gap caused by Cd substitution.

Self-hardening effect of CrAlN/BN nanocomposite films deposited by direct current and radio frequency reactive cosputtering

A CrAlN/18vol.% BN nanocomposite film was deposited on substrate by reactive co-sputtering. The films showed an increase of about 30% in indentation hardness and achieved a maximum hardness of approximately 50GPa after annealing at 800°C in air. In contrast, the indentation hardness barely changed when the film sample was annealed at 800°C in nitrogen and argon atmosphere. High-resolution transmission electron microscopy (HRTEM) images revealed that the uppermost layer was characterized by amorphous materials with embedded nanocrystalline particles (occurring at less than ~50nm below surface). Energy dispersive X-ray spectroscopy (EDS) line profiles of cross-sectional thin films showed a high concentration of oxygen in the uppermost layer of the annealed sample. The indentation hardness of the air-annealed sample was measured by Ar+ ion sputtering before and after etching to the depth at 200nm from the annealed surface. The hardness decreased from approximately 48GPa to 43GPa, which was the same level as the as-deposited films. These results indicate that oxidization of the film surface could be one of the factors responsible for the self-hardening of the CrAlN/BN film.