Evaluation of piezoresistivity properties of sputtered ZnO thin films

Abstract

Zinc oxide (ZnO) thin films were deposited by RF reactive magnetron sputtering on silicon (100) substrates under different experimental conditions. ZnO films were studied before and after annealing treatment at 600 °C. The crystallinity, electrical resistivity, stoichiometry, thickness, and elastic modulus of the films were investigated. ZnO piezoresistors were produced using microelectronics processes, such as photolithography, lift-off, and reactive ion etching (RIE). Cantilever method was used to determine the gauge factor, and measurements of Temperature Coefficient of Resistance (TCR) were performed on a hotplate. The optimization of the deposition conditions produced ZnO thin films with controlled stoichiometry (ZnO), crystalline microstructure (phase wurzite, 002), high elastic modulus (156 GPa), and low electrical resistivity (0.072 ohm.cm), which are good properties for application as piezoresistive pressure microsensor. In addition, the ZnO piezoresistors had a GF of 2.6 on the deformation in the plane (100) and TCR of -1610 ppm/K up to 250 °C.

Piezoresistive property of an aluminum‐doped zinc oxide thin film deposited via atomic‐layer deposition for microelectromechanical system/nanoelectromenchanical system applications

“…Although ZnO is classified as a semiconductor, its gauge factor in this work is considerably less than that of general semiconductor materials. The gauge factor reported in a previous study for a ZnO film is 2.6 . Possible reasons for this discrepancy are the metallic electrical characteristics and the crystallinity of AZO.…”

“…The conductivity of ZnO originates from oxygen defects. ALD‐deposited ZnO is generally less crystalline than sputter‐deposited, pulsed‐laser‐deposited, and annealed ZnO . Hou et al .…”

“…Cardoso et al . measured the gauge factor of a sputtered thin ZnO film . They optimized the deposition conditions and obtained a gauge factor of 2.6.…”

Piezoresistive Response of Quasi-One-Dimensional ZnO Nanowires Using an in Situ Electromechanical Device

“…Both samples exhibit similar electromechanical change, and the decrease in the resistivity values were calculated to be 14.2 and 13.9% with a maximum applied strain of ∼4.25 and 4.34%, respectively (Figure 5b). In most of the previous studies, the gauge factor is mainly determined by bending a substrate and calculating the corresponding strain 60 or bending a nanowire, 23 which includes significant theoretical approximations. The piezoresistance is defined as the change of the resistance under applied strain and is described by a gauge factor ( G ) in eq 1Precise measurements of the gauge factor offer a much more realistic way to understand the actual response of a piezoresistive device.…”

Modeling of an Internal Stress and Strain Distribution of an Inverted Staggered Thin-Film Transistor Based on Two-Dimensional Mass-Spring-Damper Structure

“…R• 1 ε is the gauge factor of the thin-film ZnO[40]. As given in Janotti et al[41],if the uniaxial deformed effect is neglected, the potential deformations in ZnO channel areΞ d…”