Sputtering pressure dependent bolometric properties of Ni1-xO thin films for uncooled bolometer applications

Abstract

The aim of this study is to investigate the dependence of the sputtering pressure on the bolometric properties of films. In order to analyze the structural properties, X-ray diffraction and X-ray photoelectron spectroscopy studies were conducted for Ni1-xO films deposited at various sputtering pressures. As a result, it was confirmed that all of the films had a Ni-deficient non-stoichiometric structure and that the films deposited at higher sputtering pressures revealed a more crystallized structure with fewer structural defects. The variation of the structural characteristics induced by the sputtering pressure also affected several electrical properties, known as the bolometric properties, including the electrical conductivity, temperature coefficient of resistivity and 1/f noise. With increasing the sputtering pressure from 1 mTorr to 10 mTorr, the electrical conductivity decreased from 1.0x10(-2) S/cm to 2.2x10(-5) S/cm while the absolute value of the temperature coefficient of resistivity increased from 2.76%/K to 5.62%/K, respectively. In addition, the magnitude of the 1/f noise also increased with an increase in the sputtering pressure. To evaluate and compare the bolometric performance, we introduced the material figure of merit, (alpha(H)/n)(1/2)/vertical bar beta vertical bar, which was determined by both the TCR and the 1/f noise. As a result, the films deposited at a lower sputtering pressure exhibited a lower value of (alpha(H)/n)(1/2)/vertical bar beta vertical bar, implying that these films are capable of better bolometric performance. Consequently, this research reveals that the sputtering pressure is an important parameter influencing the bolometer performance capabilities of Ni1-xO films.