An improved technique for analyzing single-atom defect structures and minor electron behavior disturbance in semiconductor and other materials has been demonstrated by researchers in Japan. The time-resolved atomic force microscopy (AFM) system overcomes the time resolution limitations of currently used scanning tunneling microscopy methods.
Combining AFM with ultrashort laser pulse technology enables measurement of high-speed dynamics in a broader range of materials, including insulators, with nanometer resolution. The optical system developed by researchers from the University of Tsukuba, TAKANO Co. and UNISOKU Co. relies on a tuning fork-type cantilever for delay time modulation of two pulse lasers (532 nm, 45 ps pulse width, 500 kHz) that can be driven by an external voltage pulse generator. This arrangement eliminates the effects of thermal expansion and extracts only the force component that reflects the dynamics of the sample excited by the pump light.
The instrument successfully measured the dynamics of surface recombination and diffusion of photoexcited carriers in bulk tungsten diselenide; such measurements are difficult to obtain with time-resolved scanning tunneling microscopy owing to the effect of the tunneling current.
By synchronizing laser pulses with AFM measurements, researchers can precisely control the timing and duration of the excitation, allowing them to capture the transient behavior of materials under light stimulation. The method described in Applied Physics Express could accelerate the development of high-performance semiconductor nanostructures and other devices.
