Black Phosphorus Field Effect Transistors Albert Liu Black - PowerPoint PPT Presentation

Black Phosphorus Field Effect Transistors Albert Liu

Black Phosphorus • Synthesis Process: Red phosphorus is heated to 1000 ° C at 10kbar. 1. The red phosphorus is cooled at a rate of 100 ° C an hour to 600 ° C. 2. Red Phosphorus Structure Black Phosphorus Structure 2

Fabrication of FET Transistors • Fabrication Process: 1. Thin flakes of Black Phosphorus peeled from bulk crystal 2. Flakes deposited on silicon wafer with SiO 2 layer in between 3. Metal (Cr, Au) contacts deposited on top of flakes by evaporation 3

Drain Current Modulation • Large drain current modulation observed • Large subthreshold swing observed (~5V per decade) V ds = 10mV (red curve) and 100mV (green curve) 4

Hall Coefficient • The Hall coefficient is given by (for electrons): • Positive (negative) hall coefficient was observed for negative (positive) gate voltage 5

Drain Current Saturation • Device parameters: – Device thickness: 5nm – Oxide thickness: 90nm – Channel length: 4.5microns – Channel width: 2.3microns V g = -30V (black), -25V (red), -20V (green), -15V (blue) 6

Sheet Resistance • The sheet resistance R S is defined by: 7

Mobility Temperature Dependence • Above 100K, the mobility follows a power law: where 8

Citation Nature Nanotechnology 9, 372 – 377 (2014) 9