Properties of Highly c-axis Oriented Single-crystalline ZnO Layers Grown by Sputter Epitaxy for Hydrogen Gas and UV Sensors

Abstract

We have previously developed ultra-high vacuum RF magnetron sputtering systems. They can produce high-quality single-crystalline compound semiconductor layers without grain boundaries on sapphire substrates. We aim to utilize these semiconductor layers in high-sensitivity sensor devices used for detecting leakage hydrogen gas (H2) from storage facilities and for early finding UV irradiation from accidental hydrogen flames. This study demonstrates the sensitivity of our single- crystalline zinc oxide (ZnO) layers to detect H2 and UV irradiation. In the result, the H2 sensor showed sufficient sensitivity to detect up to 5 ppm of H2. Moreover, the UV sensor could detect UV irradiation of 0.01 mW/cm2 at wavelength of 360 nm. Although as-grown single-crystalline ZnO layers is used without employing any sensitivity-enhancement techniques, these sensors could achieve the sensitivity equal to that of commercial devices. Thus, we considered that our single-crystalline ZnO layers using sensitivity-enhancement techniques could yield ultra-high sensitivity devises.

Keywords

• hydrogen gas sensor
• uv sensor
• zinc oxide (zno)
• sputter epitaxy
• single-crystalline layer.