New Mechanism of DC Friction Generation Based on Quantum Tunneling Effect

introduction

Mechanical energy-electric energy conversion technology is considered to have broad application prospects, and has great market potential especially in the self-power supply of miniaturized sensors, wearable electronic devices and portable devices. Among them, the friction nano power generation technology (TENG) has made remarkable progress. Conventional friction nano-power generation technology is based on the frictional electrification between dielectric materials and is often able to obtain high voltage (static charge accumulation). However, due to the high impedance of commonly used polymeric materials, the instantaneous current generated based on the principle of dielectric displacement current is often very weak. At the same time, the AC power generated by it must be converted to DC power for use.

Result introduction

In 2017, Canada's University of Alberta's Canada Excellent Research Chair, the national "external thousands of people plan" expert Thomas Thundat's group of doctoral students Jun Liu (Liu Jun) in an accidental In the conductive atomic force microscopy (C-AFM) experiment, it was found that there is a special continuous direct current generation phenomenon in the metal-two-dimensional semiconductor material friction system (J. Liu, et al. Nature nanotechnology 13 (2), 112). Recently, Dr. Liu Jun et al. discovered the exponential decay relationship of DC current with the thickness of insulator in metal-insulator-semiconductor friction system through the precise regulation of the thickness of interfacial oxide layer by atomic layer deposition (ALD), and verified the quantum of frictional direct current. Tunneling mechanism. Based on this discovery, they successfully verified the DC generator prototype of silicon-based materials in a macroscopic system. The 1-2 nm oxidized thin layer on the surface of the silicon material provides a natural electron tunneling channel with a continuous DC current density of up to 10 A/m2. The results were published online at Nano Energy under the title "Sustained electron tunneling at unbiased me tal-insulator-semico nductor triboelectric contacts". The cooperation unit consists of Prof. Ken Cadien, Professor of the Department of Materials, University of Alberta, Professor Jungchul Lee, Professor of Sogang University, Korea, and Professor Hu Zhiyu, Professor of the “Thousand Talents Program” of Shanghai Jiaotong University.

Graphic guide

(a) Schematic diagram of conductive atomic force microscopy (C-AFM)

(b) Friction DC C-AFM output signal of p-type silicon sample (probe force influence on current output)

(c) Effect of probe force on probe-sample contact area and deformation

(d) Effect of effective oxide thickness on C-AFM current output value

(e) Macro system test schematic, demonstration probe for multimeter probe

(f) and (g) are reciprocating friction and continuous rotating friction diagrams, respectively

(h) and (i) are short-circuit current output signals for reciprocating friction and continuous rotating friction, respectively

(j) The effect of the thickness of the Si oxide layer on the output current, the exponential decay tendency is consistent with the quantum tunneling mechanism of electrons

Figure 2 Voltage output characteristics of friction DC

(a) and (b) are open circuit voltage output signals for reciprocating friction and continuous rotational friction, respectively

(c) and (d) are the interface energy bands in the friction (unbalanced) and stationary (balanced) states, respectively.

(e) Effect of external bias on output current in C-AFM system

(f) Effect of thickness of Si surface oxide layer on open circuit voltage and interface electric field

Fig. 3 Effect of metal work function on the direction of interface potential difference

(a)-(c) The effect of probes of copper, gold and aluminum on the potential difference of the friction interface

Fig. 4 Characterization of the prototype of silicon-based friction DC motor

(a) Current and voltage output of single-pin friction system under different loads

(b) Current density and power density output of single-needle friction systems under different loads

(c) A single-needle system that charges the capacitor on a silicon material to charge the capacitor

summary

The discovery of the direct current effect based on the quantum tunneling effect in the metal-insulator-semiconductor friction system opens up new ideas for the utilization of triboelectricity and has a deeper exploration of the basic physics of the friction interface. The use of its principle for scale exploration has great application prospects.