Ti Doped Diamond Like Carbon Films: Piezoresistive Properties and Carrier Transport Behavior

doi:10.15541/jim20240005

Abstract

Abstract:

Diamond like carbon (DLC) film was a promising candidate for microelectromechanical system (MEMS) piezoresistive sensors owing to its excellent mechanical properties and sensitivity. The effects of carrier transport behavior and the role of operating conditions (such as temperature, humidity, etc.) on piezoresistive performance of metal-doped DLC were still unclear. In this work, Ti doped diamond like carbon (Ti-DLC) films with Ti atom fraction ranging from 0.43% to 4.11% were prepared using high-power pulse magnetron sputtering, where the high-throughput conception was introduced for film deposition. Effects of the doped Ti content on microstructure, electrical behavior and piezoresistive properties of the films were studied under various humidity environments. The results indicated that the doped Ti atoms were uniformly dissolved in the diamond like carbon matrix, accompanying typical amorphous characteristics for the Ti-DLC films regardless of Ti atom fraction changing from 0.43% to 4.11%. Furthermore, all the Ti-DLC films demonstrated distinct semiconductor feature, where the electrical resistivity was reduced with the increase of temperature in the range of 200-350 K. Particularly, the carrier transport was dominated by Mott type conduction with three-dimensional range hopping conduction from 200 to 270 K, while the thermal activation transport served as the conductive mechanism in the temperature range of 270-350 K. For the Ti-DLC films, the highest gauge factor (GF) was 95.1, and GF value increased with increasing relative humidity from 20% to 80%. This can be explained from reduction of the average distance between conductive cluster by introducing Ti atoms and a change in electrical resistance caused by adsorption of water molecules.

Key words: Ti doping, diamond like carbon (DLC) film, electrical property, variable humidity, piezoresistive behavior

CLC Number:

TQ174

ZHAO Zhihan, GUO Peng, WEI Jing, CUI Li, LIU Shanze, ZHANG Wenlong, CHEN Rende, WANG Aiying. Ti Doped Diamond Like Carbon Films: Piezoresistive Properties and Carrier Transport Behavior[J]. Journal of Inorganic Materials, 2024, 39(8): 879-886.

Figures/Tables 11

Fig. 1 Cross-sectional SEM images for Ti-DLC films Ti atom fractions are (a) 0.43%, (b) 0.97%, (c) 2.24%, and (d) 4.11%

Fig. 2 XPS spectra of Ti-DLC films (a) Cls spectra; (b) sp2/sp3 ratio

Fig. 3 Raman detection for Ti-DLC films (a) Raman spectra; (b) Fitting results of ID/IG, G-peak position and GFWHM; Ti content in atom fraction

Fig. 4 Phase structure, microstructure and EELS analyses for Ti-DLC films (a) XRD patterns of Ti-DLC films; (b) HRTEM image and corresponding SAED of Ti-DLC film with 4.11% Ti; (c) EELS spectrum of Ti-DLC film with 4.11% Ti; Ti content in atom fraction

Fig. 5 I-V plots for Ti-DLC films at different temperatures Ti atom fractions are (a) 0.43%, (b) 0.97%, (c) 2.24%, and (d) 4.11%; Colorful figures are available on website

Fig. 6 Electrical properties of Ti-DLC films at different temperatures (a) R-T behaviors; (b) TCR

Fig. 7 R-T fitting results of Ti-DLC films within different temperature ranges (a) lnR and T-1/4; (b) lnR and T-1

Fig. 8 Electrical properties of Ti-DLC films under various relative humidities (a) Resistance; (b) GF; Ti content in atom fraction

Fig. S1 Schematic diagram of the deposition equipment for Ti-DLC film and specific sample positions

Fig. S2 Piezoresistive testing device

Fig. S3 Wetting behaviors of Ti-DLC films with different Ti contents (a) Water-contact angle; (b) Surface energy; Ti content in atom fraction

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