Heterojunction-Type Hydrogen Sensor Based on Silicon Nanoconvexity Induced by Femtosecond Laser

Simple CuO-based hydrogen sensors at room temperatureusually needto be used with precious metals. In this work, a p-CuO/n-Si hydrogen sensor with a nanoconvexity structureis conceived as an effective room-temperature hydrogen sensor withoutthe precious metal decoration. The convexity-like nanostructure wasinduced on the n-Si substrate surface using the femtosecond(fs) laser direct writing technique. After hydrofluoric acid (HF)treatment, a layer of a p-CuO nanofilm was sputteredto fabricate a pn-junction hydrogen sensor (CuO/fs-Si). The sensorcan work at room temperature when hydrogen concentration ranges from100 to 30,000 ppm. At a hydrogen concentration of 10,000 ppm, theresponse time constant is 216 s. As a comparison, it is found thata pn-junction-type CuO/Si sensor without fs laser processing (CuO/Si)cannot detect hydrogen with a concentration of less than 10,000 ppm.The nanostructured Si surface improves the sensitivity of the sensorand reduces the detection limit. Operating at room temperature reducesthe energy consumption of the sensor and improves applicability. Asimple p-CuO/n-Si bilayer structureprovides an alternative idea to develop miniaturized, low-power, compatible,and integrated hydrogen sensors.