An atomic Force Photon Scanning Tunneling Microscope (AF/PSTM) is reported here

which uses a shift in resonance frequency to control the distance between a sample and a fiber probe. For self-oscillating tapping mode AF/PSTM applications

a sharp end and large conical angle optical fiber tip with an apex diameter smaller than 100 nm and a cone angle of 60～90° is fabricated. The tip is mounted on a piezo

then the piezo is placed in a positive feedback circuit to excite the probe to oscillate. The oscillation frequency of the tip is demodulated by a PLL

and its value is maintained a constant by controlling the negative feedback loop of the Z piezo to track the sample surface. Both theory and experiment are carried out to compare the externally excitation mode and self-oscillating mode. Results show that the self-oscillation mode reduces the response time of the tip in theory

and the bandwidth of self-oscillating mode in proposed AF/PSTM is 50 Hz in experiments

which is higher an order of magnitude than that of externally excitation mode response. A sample of grating is scanned by proposed instrument with a scanning rate of 1 Hz

and results demonstrate that the topography and optical images obtained by self-excitation mode have clearer contrast than those obtained by externally excitation mode. Besides faster response

the self-oscillating mode can improve the system resolution by increasing Q without effecting on the system response speed.