Research Of Photocurrent Mapping And Laser Diret Writing System Based On 2-axis Galvanometer

Micro-nano semiconductor materials represented by one-dimensional nanowires and two-dimensional nano-sheets have become an important research direction of optoelectronic materials with their unique photoelectric properties.The research on the fabrication of prototype electronic devices based on single nanowires and single nanosheets and their photoelectric response characteristics has become a research hotspot.In terms of device fabrication,electron beam exposure is widely used in the processing of micro devices due to its high line width accuracy.Compared with electron beam direct writing technology,laser direct writing has the advantages of low cost and low environmental requirements.In terms of response characteristics,position-dependent photocurrent imaging technology provides great help for studying the transmission,separation and recombination processes of photogenerated carriers in micro/nano optoelectronic devices,as well as further optimizing the device structure and improving the photoelectric conversion efficiency of devices.Both of the above aspects can be realized by beam movement or displacement of the stage.This paper mainly designs and builds a micro-area laser direct writing and photocurrent scanning imaging system based on two-dimensional galvanometer for laboratory micro-nano device fabrication and photocurrent position imaging test.The system has a faster scanning speed than a conventional stage-based photocurrent scanning imaging system.We first use the programmable reconfigurable I/O function of the Myrio-1900 device to perform LabVIEW programming to complete the handle control and realize the automated movement observation of the sample to be tested.Then,the LabVIEW program controls the two-dimensional galvanometer to perform laser deflection,so that the beam is scanned on the surface of the photoresist.Based on the optimized exposure parameters,the objective lens is kept at a 50× objective lens with a NA value of 0.5 and the sample stage remains stationary.Laser direct writing with a writing range of ± 30 ?m,writing a 50 ?m × 50 ?m square takes about 10 seconds.Next,we use a standard silicon photodetector to validate the photocurrent scanning imaging.Through the scanning of the light beam in the photosensitive area of the standard photodetector,the current data is measured by the digital power meter,and the photocurrent is recorded in real time,so that the scanning photocurrent imaging function is displayed point by point.We tested the graphene/tungsten disulfide/silicon(Gr/WS2/Si)heterojunction optoelectronic devices,with a device response time of ms,achieving fast data with 10,000 photocurrents per frame in 240 s Imaging.In order to further optimize the system,the photocurrent imaging image and the device to be tested have a higher degree of matching.We add the reflection collection module in the system.At the same time,in order to reduce the impact of noise on imaging,we use a low-noise current preamplifier and a lock-in amplifier to obtain high signal-to-noise ratios imaging of weak photocurrent.