CCD272-64 and GSENSE400BSI-GP CMOS quantum efficiency measurement in EUV and VUV

Abstract

We have measured the spectral quantum efficiency of several digital detectors in two spectral ranges, namely vacuum ultraviolet (VUV, and extreme ultraviolet (EUV, 10-58 nm) wavebands. We used monochromatic synchrotron radiation from the VEPP-4M storage ring (INP, Novosibirsk) to investigate the spectral response of GSENSE400BSI-GP CMOS which have been specially designed for optimum VUV sensitivity, as well as the WSO-UV project's custom deep cooled CCD272-64 sealed within a hermetic contaminant-protective stainless-steel enclosure with a VUV-transparent entrance window. The CMOS GSENSE400BSI-GP sensitive surface has four types of different pretreatment: (i) small boron implantation dose, weak annealing; (ii) small boron implantation dose, strong annealing, (iii) large boron implantation dose, weak annealing; (iv) large boron implantation dose, strong annealing. These VUV optimised CMOS sensors have higher spectral sensitivity and higher quantum efficiency in the 112-180 nm spectral range, compared to a commercial CMOS which is typically optimised for the best performance at visible wavelengths, but at longer wavelengths GSENSE400BSI-GP sensitivity decreases. The measurements have revealed that stronger annealing can slightly increase the CMOS spectral sensitivity, while large boron implantation dose decreases the sensitivity of the CMOS sensors. With relation to quantum efficiency figures, CCD still prevails in the VUV while recent advances in CMOS technology could make CMOS more preferable in the EUV range.