Photo-EMF Sensitivity of Porous Silicon Thin Layer–Crystalline Silicon Heterojunction to Ammonia Adsorption

Abstract

A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light.

Surgical management of breast cancer in China: the Fudan University Shanghai Cancer Center experience

“…Besides, many physical parameters of the PSi are proven to be sensitive to gas surroundings which are the basis for gas sensor design [109]. Y. Vashpanov et al [84] first implemented the concept of PV self-powered gas sensing using PSi/Si heterojunction, which was fabricated by forming a thin (12 μm) layer of PSi on the silicon wafer by electrochemical etching in HF-based solutions. As shown in Fig.…”

“…As shown in Fig. 5a, the photo-electromotive force (photo-EMF, i.e., photovoltage) of the PSi/Si heterojunction was measured at room temperature under the light illumination as the sensing signal, and it was claimed to be sensitive to ammonia [84], ethanol/mercaptoethanol [88], and acetone [97]. In one of the works, the dependences of the photo-EMF on the light wavelength, the light intensity (characterized by the illumination level) and the NH 3 concentration were preliminarily investigated ( Fig.…”

Porous silicon gas sensors

“…A new method for using photo-electromotive force (Photo-EMF) in the detection of gas and for controlling sensitivity is proposed (Vashpanov et al ., 2011). Photo-EMF on the heterojunction between the PSi thin layer and the crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber.…”

Influence of Illumination on Porous Silicon Formed by Photo-Assisted Etching of p-Type Si with a Different Doping Level

“…Porous silicon (por-Si) has been receiving a great deal of attention due to its interesting physical and optical [1] properties and promising potential technological applications in the fields of sensing [2,3], Li-ion batteries [4], and solar cells [5]. The morphology of the silicon wafer may be modified by electrochemical wet etching [6][7][8], galvanic etching [9][10][11], or metal-assisted chemical etching (MACE) [12,13] to produce pores, nanowires, and microstructures.…”