Investigations on photo-mechanical and photo-thermo-mechanical strain variations in amorphous selenium using fiber Bragg grating sensor

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

“…The dark current density measured at different bias voltage remains a 10 −7 A/mm 2 order of magnitude (Figure 4b), although the dark current rises with increasing bias voltage. Further, X-radiation responsive characterization with the current gain (G) of 2.52× of sample appears at weak electrical field (0.25 V/mm–1.25 V/mm), and the strong electrical field is not required by a-Se thin films comparing with driving electrical filed (tens of volts per micron) of a-Se thick films [2,4,5,7,8]. It can be seen from Figure 4c that the photogeneration current of a-Se thin films has a rapid response without obvious tailing both X-ray on and X-ray off, suggesting the low trap effects and high deposition quality of thin films [19].…”

“…The thermal evaporation method is a good way to prepare a-Se films [4,5,6], and the background vacuum operating 10 −3 Pa to 10 −4 Pa is a current preparation condition [7,8,9]. However, it is well known that a high vacuum degree implies expensive equipment requirements and lots of vacuum preparation time, which apparently increase the production costs.…”

“…By comparison, the vacuum degree of 10 −2 Pa is very easy and quick to be achieved for any vacuum equipment. On the other hand, several reports have preferred to investigate the a-Se thick films with a thickness of tens of microns to hundreds of microns [4,5,6,7,10], since a-Se thick films can absorb more X-ray energy and thus produce a higher photocurrent; further, the systematic research on the a-Se thin films with the thickness of a few microns is rare [8]. Nevertheless, the low crystallization temperature, 40–50 °C, is a fatal disadvantage of a-Se thick films, as it seriously restricts its practical applications [11,12].…”