Abstract
In recent years, flexible photodetectors are widely utilized in wearable devices and other special applications due to the advantages of outstanding flexibility, superb electronic stability and high detectivity. One-dimensional nanostructures of semiconductors provide many opportunities and capabilities for applications in flexible photodetectors as they may possess great photoelectric properties. Zinc selenide (ZnSe), a II–VI compound n-type semiconductor with a wide direct bandgap of ~2.67 eV (~465 nm), has higher sensibility of blue/UV light, comparing to other intrinsic (Si) and III-V semiconductors (GaAs). In the present research, single-crystalline ZnSe nanowires with high aspect ratio were grown on silicon substrate in a double tube system by chemical vapor deposition (CVD). A single ZnSe nanowire photodetector with a meatal-semiconductor-metal (MSM) structure was fabricated by typical photolithography procedures. The basic photoelectric properties of a single nanowire under 405 nm blue laser irradiance with different power intensities and bias voltages were investigated. For flexible device, ZnSe nanowires were successfully transferred on PDMS/polyimide substrate via the contact printing method. Au interdigitated electrodes were then deposited on ZnSe nanowires to form a MSM structure. With same measurement conditions, the as-fabricated photodetector exhibits high on/off photoswitching characteristic and fast photoresponse speed both on rise and on fall. In addition, the highly transparent polyimide substrate provides excellent mechanical flexibility so that our photodetector can be effectively operated under bending up to 180o. The excellent performance indicates that the high quality ZnSe nanowires based flexible photodetector on transparent polyimide substrate may lead to practical applications.