Enabling Ultrasensitive Photo-detection Through Control of Interface Properties in Molybdenum Disulfide Atomic Layers

Abstract

The interfaces in devices made of two-dimensional materials such as MoS2 can effectively control their optoelectronic performance. However, the extent and nature of these deterministic interactions are not fully understood. Here, we investigate the role of substrate interfaces on the photodetector properties of MoS2 devices by studying its photocurrent properties on both SiO2 and self-assembled monolayer-modified substrates. Results indicate that while the photoresponsivity of the devices can be enhanced through control of device interfaces, response times are moderately compromised. We attribute this trade-off to the changes in the electrical contact resistance at the device metal-semiconductor interface. We demonstrate that the formation of charge carrier traps at the interface can dominate the device photoresponse properties. The capture and emission rates of deeply trapped charge carriers in the substrate-semiconductor-metal regions are strongly influenced by exposure to light and can dynamically dope the contact regions and thus perturb the photodetector properties. As a result, interface-modified photodetectors have significantly lower dark-currents and higher on-currents. Through appropriate interfacial design, a record high device responsivity of 4.5 × 103 A/W at 7 V is achieved, indicative of the large signal gain in the devices and exemplifying an important design strategy that enables highly responsive two-dimensional photodetectors.

Nanoscale charge transfer and diffusion at the MoS2/SiO2 interface by atomic force microscopy: contact injection versus triboelectrification

“…Lu et al [31] observed significant N-doping in thin MoS 2 films on SiO 2 , which is dominated by charge traps at the sample−substrate interface by scanning tunneling microscopy. The charge trapping at the SiO 2 −MoS 2 interface and its effects on the characteristics of the MoS 2 field effect transistors and photodetection devices have been studied [32][33][34]. Very recently, Kim et al [35] investigated the triboelectric charges of a graphene/SiO 2 system, and found that the triboelectric charges are trapped at the air-SiO 2 interface underneath the graphene and act as ghost floating gates.…”

Advanced atomic force microscopies and their applications in two-dimensional materials: a review

“…Lu et al [178] observed significant N-doping in thin MoS 2 films on SiO 2 , dominated by charge traps at the sample − substrate interface by STM. Further, the charge trapping and its effects on the characteristics of the MoS 2 field-effect transistors and photodetection devices were investigated [179,180]. Liu et al [181] claimed to generate anomalously high DC using a sliding Schottky nano-contact in a sliding semiconductor-metal contact (on MoS 2 multilayers/Ag).…”