Kun-sun Eom

Pulsed I –V measurement method to obtain hysteresis-free characteristics of graphene FETs

Current-voltage (I–V) characteristics of the graphene field effect transistors (GFETs) are measured by the dc, fast I–V (FIV), and pulsed I–V (PIV) methods and analyzed. The hysteresis and conductance in the dc measurement are affected by the sweeping bias range and direction. The I–V curves measured by the FIV method show reduced hysteresis and enhanced conductance at a faster sweeping rate, but are still affected by the sweeping bias range. By applying the PIV method, the hysteresis can be suppressed significantly while the conductance is improved by controlling turn-on, turn-off times (t on and t off) and the gate bias during t off (V base) regardless of the sweeping bias range. With short t on, long t off, and V base of 0 V, the hysteresis-free characteristics of GFETs are obtained.

Analysis and suppression of drain current drift in graphene FETs

The cause of drain current (ID) drift in graphene field-effect transistors is analyzed and a method to suppress the drift is proposed. By analyzing ID-time characteristics, a condition of reasonable gate, drain and source biases (VG, VD, and VS) is proposed to suppress ID drift. Based on this result, we find a condition for VG during off-time (Vbase), VD, and VS in pulsed I-V measurement to obtain the intrinsic ID-VG curves, and analyze the effect of Vbase on the Dirac point shift. Through an analysis of ID-time characteristics depending on VG, ID drift according to the range of VG is explained.

Bandwidth limitation of the electrolytes for DNA sequencing using nanopore sensors

DNA sequencing using nanopore-based sensors attracts considerable interests because of the possibility of ultimate sensitivity of single-molecule resolution. Due to the fast DNA translocation speed on the order of microsecond, the sensor requires a wide bandwidth exceeding a megahertz. Such a high frequency signal transmits through the electrolyte and the sensor measures ionic current changes. The electrolyte is essential to dissolve DNA sample into the sensor. However, the bandwidth of the electrolyte has not been considered yet. This study presents the bandwidth limitation of the electrolyte and we believe it should be considered when using DNA sequencing method via high frequency signal detection through the electrolyte.