Photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid.
The authors present an optically based method combining photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid. The frequency spectrum of a silicon cantilever measured in water over frequencies ranging up to 10 MHz shows that the method allows us to excite and detect higher modes, from fundamental to fifth flexural, without enhancing spurious resonances. By reducing the tip oscillation amplitude using higher modes, the average tip-sample force gradient due to chemical bonds is effectively increased to achieve high-spatial-resolution imaging in liquid. The method's performance is demonstrated by atomic resolution imaging of a mica surface in water obtained using the second flexural mode with a small tip amplitude of 99 pm; individual atoms on the surface with small height differences of up to 60 pm are clearly resolved.
Nishida
Shuhei
S
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Kobayashi
Dai
D
Sakurada
Takeo
T
Nakazawa
Tomonori
T
Hoshi
Yasuo
Y
Kawakatsu
Hideki
H