Influence of negative metal ion bombardment on the properties of ITO/PET films deposited by dc magnetron sputtering

Abstract

Transparent conducting indium tin oxide (ITO) thin films were deposited on a polyethylene terephthalate (PET) substrate at a low substrate temperature by dc magnetron sputtering using a negative metal ion source and an ITO target. During separate deposition runs, the cesium partial pressure was varied from 1 × 10 −3 to 2.2 × 10 -3 Pa to investigate the effect of ion beam bombardment on the surface morphological, electrical and optical properties of the films. The resistivity of ITO films decreased with P Cs and reached as low as 6.2 × 10 −4 Ω cm at P Cs of 1.7 × 10 −3 Pa. Optical transmittance compared with bare PET substrate also varied significantly with P Cs and the highest optical transmittance of 87% (at λ=550 nm) was obtained at P Cs of 1.7 × 10 −3 Pa. According to a result obtained by AFM, surface roughness of the ITO/PET film showed remarkable change from 2.8 to 1.1 nm with P Cs. However, above optimal P Cs condition (>1.7 × 10 −3 Pa), the electrical, optical property and surface morphological properties deteriorated. From SEM, AFM, and Hall measurements, relatively low resistivity and high transmittance of ITO film deposited at P Cs=1.7×10 −3 Pa is caused by an increase in charge carrier concentration and flat surface morphology with secondary negative metal ion beam bombardment.