# Improved Hydrogen-Sensing of TiO2 Schottky Device Through Schottky Barrier Height Modulation

## TL;DR

This study improves hydrogen sensing in TiO2 sensors by adjusting the Schottky barrier height through controlled annealing.

## Contribution

A novel method of modulating the Schottky barrier height in TiO2 sensors via annealing temperature is introduced.

## Key findings

- Annealing at 500 °C produced the highest gas-sensing response of 242 to 1 ppm H2.
- The sensor's performance is linked to the Schottky barrier height and oxygen vacancy concentration.
- Three distinct sensing regimes were identified based on the gas-sensing mechanism analysis.

## Abstract

Adjusting the Schottky barrier height is an important approach to enhancing the gas-sensing performance of TiO2 Schottky sensors. In this study, micro TiO2 nanotube Schottky sensors were fabricated via magnetron sputtering and anodic oxidation, with their Schottky barrier height adjusted by varying the annealing temperature. The morphology, phase composition, oxygen vacancy concentration, band structure, and Schottky junction of the samples were investigated using SEM, GIXRD, EPR, Hall effect measurements, XPS, I-V curves, and AC impedance. The sensor annealed at 500 °C demonstrated the highest gas-sensing response, outperforming sensors treated at other temperatures by over 100 times. Its response value to 1 ppm H2 was 242. The annealing temperature significantly affects the TiO2 phase and oxygen vacancy concentration, resulting in the highest Schottky barrier height in the 500 °C-annealed sensor, which contributes to its superior sensing performance. AC impedance measurements revealed no significant Fermi-level pinning in TiO2. Based on the gas-sensing mechanism analysis, the response of the TiO2 sensor can be divided into three regimes: Schottky junction control, TiO2 resistance control, and co-control.