Preparation of zinc oxide films containing Be and N atoms by radio frequency magnetron sputtering

ZnO films containing both Be and N atoms were deposited on (0001)-sapphire substrates heated at 250 °C, by using a target consisting of Be sheets placed on ZnO powders. There are only ZnO (0002) peaks observed in the X-ray diffraction (XRD) patterns of the ZnO films. As the power of radio frequency (RF) in sputtering increases, the c-axis lengths of the sputtered ZnO films decrease significantly, and the concentration of Be atoms in the ZnO films increases remarkably. The presence of Be and N atoms is confirmed in the ZnO film prepared at 70 W, from X-ray photoelectron spectroscopic (XPS) measurements. For the ZnO film prepared at 70 W, the binding energy of Be 1s and of N 1s is evaluated to be 114.0 and 398 eV, respectively. The concentration of N atoms is as low as 1% for the ZnO film containing no Be atoms, whereas the high concentration of 7% N atoms is attained in the ZnO film containing 4% Be atoms. The ZnO films prepared at 120 W or more are insulators, and the ZnO film doped with N atoms alone is an n-type semiconductor. The ZnO film containing both 4% Be and 7% N atoms is a p-type semiconductor with a resistivity of 45 Ω cm.