I-V shifts Dimension3100 with TUNA

virggis posted on Mon, Dec 2 2013 8:18 AM

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Hi all,

we have zero point shifts in our Dimension 3100/Nanoscope IVa system with Extended TUNA module. I attached graph illustrating the shifts. Reference measurements of commercial diode were made with Keithley 2601 source meter and I-V curves goes through zero point in booth cases: diode forward biased and reverse (black and red curves). When the same diode is connected to SPM (one end connected to universal connector socket on Ext.TUNA module, the other one to sample chuck) I-V curves misses zero point (I=0, U=0) and the sign of the current at U=0 depends on diode connection (forward or reverse). If we forward biased the diode at U = 0, I = 0.5 pA (blue curve); if reverse biased at U = 0, I = - 0.5 pA (green curve).

My question is it normal for D3100 with TUNA module, or we have some signal in electronic circuit?