1. Form Quantum Wires and Quantum Dots on Surfaces
4/27/2017
Form Quantum Wires and Quantum Dots on Surfaces
with Vapor Deposition Techniques
David Ji
Feb. 7th, 06

2. Part One: Quantum Wires
A. Growth of Quantum Wires Pinned on Substrate
1.vapor–liquid–solid (VLS)
Three Steps:
Alloying process
Nucleation of precursors
Axial growth
Why? Growing under the catalyst?
Vapors diffuse and condense at the existing solid/liquid interface, due to that less energy will be involved with the crystal step growth as compared with secondary nucleation events in a finite volume.
Ref: 3165 J. Am. Chem. Soc. 2001, 123,

3. 2. solid–liquid–solid mechanism (is not Vapor deposition)
SiNW as an example
alloy
heating
Gas cooling
Ni supersaturated
Amorphous nanowire!
Inert gas flow plays important role in the formation of the nanowire
Ref: Chem. Phys. Lett. 323 (2000) 224.

4. 3. Standing in Hard Template
prepare well-aligned NWs arrays by CVD without catalyst.
Templates:
Mesoporous template
Nano porous alumina template
Advantages:
a. The size and shape of SiNWs can be controlled and vary over a wide range
b. Well template-isolated nanowires arrays
c. Sharp tips and perfect lattices can be obtained
Ref: Chemical Physics Letters 374 (2003) 542–547

5. B. Suspended NW Lying on Substrate
Suspended Carbon Nanotube Quantum Wires with Two Gates
Electron beam lithography (EBL): define the local-gate pattern, S/D pattern, pattern catalyst islands.
Source (S) and drain (D) metal electrodes, a metal local gate (VGL) at the bottom of the trench and a global Si back gate (VGB).
Show different properties compared with pinned CNT on substrate.
Ref: small 2005, 1, No. 1

6. In order to be capable of being incorporated into devices,
C. Challenges in Synthesizing NW:
In order to be capable of being incorporated into devices,
Controlled orientation and size of the grown nanostructure required.

7. Part Two: Quantum Dots (QD)
Formation Mechanism:
Stranski–Krastanow (SK) growth mode responsible
Applications: Optical and electronic properties
About quantum laser:
Characteristics would be improved dramatically due to reduction of dimensionality of the electron motions in quantum nanostructures, proposed by Arakawa and Sakaki
This is why people like Zero dimensionality
Ref: Appl. Phys. Lett., vol. 40, pp. 939–941, 1982.

8. Organometal chemical vapor deposition (OMCVD)
Hot Research Field:
Semiconductors QD. ex. binary & tertiary compound from IIIA and IVA. InAs/GaAs dots extensively investigated.
GaSb/GaAs attracted interest for its potential application in capacitors.
Synthesis Method:
Organometal chemical vapor deposition (OMCVD)
ex. In forming QD compound containing Ar. ArH3 was replaced by tertiarybutylarsine (TBAs)
Molecular beam epitaxy (MBE)
Creating a 'molecular beam' of a material which impinges on to the substrate.
Ref:
Physica E 13 (2002) 1181 – 1184
Appl. Phys. Lett., Vol. 82, No. 6, 10 February 2003