Development of a scanning probe microscope compact sensor head featuring a diamondprobe mounted on a quartz tuning fork

Abstract

The development of a compact scanning probe microscope sensor head, designed to mountaround a standard microscope objective, is described. The instrument features a quartztuning fork with an innovative diamond probe. This configuration has a number of keyadvantages: (i) the displacement of the probe relative to the sample surface isself-sensing, (ii) the diamond tip is robust and (iii) it is designed to accommodate futurenear-field optical applications. A custom current-to-voltage amplification circuit wasconceived to compensate for the inherent capacitance of the quartz tuning fork. Amechanical design has been realized to allow positioning of the probe relative tothe microscope objective and the swift exchange of quartz tuning fork sensors.Additionally, the design permits rotation of the sensor so that its orientationwith respect to the sample may be changed. To demonstrate the feasibility andresolution of the system, a semi-insulating GaAs wafer has been imaged to reveal thepresence of InAs quantum dots (QDs). The QDs can be seen clearly in the imagepresented here, with their height profiled to be typically 6 nm. Cross-sectionalanalysis of the raw data gives a background RMS value of 0.6 nm for a profile2 µm in length.