Experimental and theoretical investigation of transparent and conductive B doped ZnO film

Abstract

The properties of boron doped ZnO (BZO) films are investigated by the pulsed DC magnetron sputtering technique and the plane wave pseudo-potential method based on the density-functional theory. Highly conductive and transparent BZO thin films are prepared using a B2O3:ZnO ceramic target. The effects of the substrate temperature on the structureand electrical and optical properties are systematically investigated. The results show that by increasing the substrate temperature appropriately, the crystallinity, grain size, and carrier mobility of BZO film are improved, and the resistivity is reduced. BZO films of low resistivity (7.03×10-4 Ω·cm) and high transmittance (89%) from 400–1100 nm are achieved at an optimal substrate temperature of 200 ℃. The theoretical results show that B is doped in ZnO mainly in three forms, i.e., in the forms of substitutional BZn atoms, octahedral interstitial site (BIO), and tetrahedral interstitial site (BIT). Among them the formation energy of BZn defect is lowest, and its concentration may be the highest in all the sample concentrations. After incorporation of B, the Fermi level goes through the conduction band. The sample shows a typical n-type metallic characteristic and the optical band gap increases significantly. The carriers originate from the orbits of B 2p, O 2p and Zn 4s.