Silicon And Porous Silicon – Based Extended Gate Field Effect Transistor For pH And Cations Sensor

Following the advances in biochemical sensors based on porous silicon (PSi) in the late 20th century, several studies have been carried out to take advantage of the intrinsic properties of PSi for development of biochemical sensors. The commercial ntype silicon (Si) has been used in two forms, namely, flat surface and porous layer based on extended gate field effect transistor (EGFET), as sensors for the pH and cations (Na+, K+, Mg2+, and Ca2+). This study aim is to improve the low silicon sensitivity as a cations sensor by increasing the surface area in a cheap and simple way

Effect of gamma irradiation dose on the structure and pH sensitivity of ITO thin films in extended gate field effect transistor

Even though several studies have demonstrated the use of Indium Tin Oxides (ITO) as an extended gate field effect transistor (EGFET), the effect of different doses of gamma radiation on the intrinsic properties of the ITO films has not been considered. This study investigates the effect of gamma irradiation on the structural, optical, morphological and electrical properties as well as pH sensitivity (as an extended gate field effect transistor) of ITO thin films. ITO thin films with thickness of 400 nm were prepared using a radio frequency sputtering technique. The samples were then subjected to various doses of gamma radiation from a Co-60 radio-isotope (0.5 kGy, 1 kGy, 1.5 kGy, and 2 kGy). The structural and morphological changes as well as transmission and absorption of the thin films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field-Emission Scanning Electron Microscope (FESEM) and UV–Vis spectrophotometry, before and after irradiation. The irradiated ITO thin films were then used as an extended gate field effect transistor to determine its ability to improve sensitivity as pH sensors. The grain size and transmittance in the range 300–900 nm of the ITO films were found to decrease with increasing gamma irradiation dose. In contrast, the uniformity and surface roughness of ITO thin films increased with increasing gamma radiation dose due to the formation of lattice defects. Moreover, the electrical resistance of the thin films increased with increasing dose because of the low current density and high number of surface defects associated with irradiation. The pH sensitivity of the ITO thin films improved after irradiation, possibly due to the concomitant increase in surface roughness with increasing radiation dose. The improvements in the pH sensitivity of ITO thin films after irradiation justify their potential use as pH sensors. Keywords: Indium Tin Oxide, Thin films, Gamma irradiation, Optical band gap, X-ray diffraction, EGFET, pH senso