TABLE 13.2

Main Different Fabrication Methods of WBG Nanostructures and Their Highlights and Limitations

Classification

Technique

Highlights

Limitations

Direct Growth

Methods

Electrochemical

Deposition

Simple, fast, and low-cost

method;

The large surface area of

treatment

Possible instability of voltage and

current;

Seeding-Annealing-

Growth

Low-temperature;

Well-controlled morphology

Quality of nanostructures in

different reaction parameters

Hydrothermal or

Solvothermal

Scalability;

Well-controlled morphology

Usually requires high synthesis

time

Bottom-Up

Methods

Vapor-Liquid-Solid

Mechanism

The growth parameters of

nanowires can be

manipulated and controlled

by varying the conditions of

reactions

The formation of defects due to

the chosen catalyst

Chemical Vapor

Deposition

Catalyst-free reaction;

High-quality crystalline

nanowires

High-temperature vacuum-

chamber process

Thermal Evaporation

Simple process;

Low-cost method

Morphology control

Molecular Beam

Epitaxy

Suitable for wide materials

system

Expensive technique;

Low growth rates

Sol-Gel Technique

Simple process;

Highly controlled approach

Expensive raw materials;

Time-taking process

Top-Down

Methods

Photolithography

Highly aligned

nanostructures;

Control of the electrical

properties

Resolution of nanostructures due

to the limitation of optical

systems (which can be worked

around in a derivative

technique)

Focused Ion Beam

Very precise for nanostructure

fabrication;

A pre-prepared nanostructure

patter is not required

Low yield as it is a serial process

Electron Beam

Lithography

High resolution

Low yield as it is a serial process;

Not ideal for large-scale

fabrication

FIGURE 13.4

Schematic mechanism of the preparation of WBG semiconductors through the hydrothermal technique.

212

Bioelectronics