Electronics

The STM-electronics are based on a digital design. The DSP controlling the 'digital' feedback loop (maximum speed 200.000pixels/s) is electronically decoupled from the analog I/O board, which provides 6 D/A outputs (20bit, >200kHz, +/- 10V), 4 A/D inputs (18bit, >200kHz, +/-10V) and 32 digital I/O ports (16 input, 16 output). The DSP is able to provide a lock in amplifier for the first and second harmonics of the tunneling current by software. All features are controlled by a Windows PC using a high speed USB2.0 link. The HV-amplifier has 3 channels with dual voltage bipolar output (±200V, 60kHz, RMS: 1mV). Each channel offers modulation and offset voltage input and manual gain settings (with digital readouts) of 1x, 3x, 10x, 30x. The preamplifier (DLPCA-200) allows to set the required gain with the digital I/O of the DSP-board (10³ … 10¹¹ V/A, bandwidth: 500kHz … 1.2kHz). With a typical scan speed of about 100nm/s an image of (30nm)² with (256 pixel)² is acquired in less than 3min (typical @6K).

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