Local doping of two-dimensional materials
This disclosure provides systems, methods, and apparatus related to locally doping two-dimensional (2D) materials. In one aspect, an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a 2D material disposed on the second insulator is formed. A first voltage is applied between the 2D material and the substrate. With the first voltage applied between the 2D material and the substrate, a second voltage is applied between the 2D material and a probe positioned proximate the 2D material. The second voltage between the 2D material and the probe is removed. The first voltage between the 2D material and the substrate is removed. A portion of the 2D material proximate the probe when the second voltage was applied has a different electron density compared to a remainder of the 2D material.
1. A method comprising:
(a) forming an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a two-dimensional (2D) material disposed on the second insulator;
(b) applying a first voltage between the 2D material and the substrate;
(c) with the first voltage applied between the 2D material and the substrate, applying a second voltage between the 2D material and a probe positioned proximate the 2D material;
(d) removing the second voltage between the 2D material and the probe; and
(e) removing the first voltage between the 2D material and the substrate, a portion of the 2D material proximate the probe in operation (c) having a different electron density compared to a remainder of the 2D material.
2. The method of claim 1 , wherein the 2D material comprise about 10 monolayers of material or less.
3. The method of claim 1 , wherein the 2D material comprises graphene.
4. The method of claim 1 , wherein the 2D material is selected from a group consisting of molybdenum disulfide, molybdenum diselenide, tungsten disulfide, and tungsten diselenide.
5. The method of claim 1 , wherein the probe is positioned about 10 nanometers or less from the 2D material in operation (c).
6. The method of claim 1 , wherein the second voltage applied between the 2D material and the probe in operation (c) is about −100 volts to +100 volts.
7. The method of claim 1 , wherein the second voltage applied between the 2D material and the probe in operation (c) is about +5 volts or higher.
8. The method of claim 1 , wherein the second voltage applied between the 2D material and the probe in operation (c) is about −3 volts or lower.
9. The method of claim 1 , wherein the second voltage applied between the 2D material and the probe in operation (c) is applied for about 0.1 seconds to 5 minutes.
10. The method of claim 1 , wherein the first voltage applied between the 2D material and the substrate in operation (b) is about −150 volts to about +150 volts.
11. The method of claim 1 , wherein the first insulator comprises a material selected from a group consisting of silicon oxide, hafnium oxide, and aluminum oxide, wherein the second insulator comprises a material selected from a group consisting of boron nitride and a silicate mineral, and wherein the substrate comprises a material selected from a group consisting of a doped semiconductor, a layered semimetal, and a metal.
12. The method of claim 1 , wherein the first insulator has a greater band gap than the second insulator.
13. The method of claim 1 , wherein the probe comprises a conductive material.
14. The method of claim 1 , wherein the probe comprises a metal wire or a carbon nanotube.
15. The method of claim 1 , wherein the probe comprises a conductive substrate and a pattern disposed on a surface the conductive substrate comprising a conductive material.
16. The method of claim 1 , wherein the first insulator is about 10 nanometers to 500 nanometers thick.
17. The method of claim 1 , wherein the second insulator is about 5 nanometers to 300 nanometers thick.
18. The method of claim 1 , wherein the substrate has a thickness of about 50 nanometers or greater.