Development of NTU APPJ System, Measurement and Simulation of the Properties of Ga-doped ZnO films Prepared by Multiple Depositions
Date Issued
2016
Date
2016
Author(s)
Chen, Yu-Yi
Abstract
One of the advantages of the Atmospheric Pressure Plasma Jet, APPJ equipped with DC pulsed power source, is free of the vacuum chamber and is used to deposit Ga-doped ZnO(GZO)thin films in open air. By depositing small area thin films step by step, we can have a large area thin films. Recent research shows that the multi-layer deposition method, which stack materials with different characteristics together, can achieve better electrical and optical properties. However, the multilayer deposition often requires using different material as the buffer layer, which may increase the process time, tool complexity and materials cost. Here we studied the feasibility of enhancing the film properties and deposition rate by multiple depositions using only GZO, and adjusting the scanning speed and times. We find that both the deposition rate and the films properties are significantly improved. The method can be applied to other methods that involve scanning trajectory, such as spray pyrolysis. In this thesis, we conduct three-dimensional finite element simulations on conductive multilayer films to study the relationship between the reading of the four-point probe and the conductivity of the individual layers. We find that a multilayer film may be modeled as a simple equivalent circuit with multiple resistances connected in parallel for a wide range of resistivity and thickness ratios as long as its total thickness is smaller than approximately half of the probe spacing. As a result we may determine the resistivity of each layer sequentially by applying the four-point probe, with the original correction factor π/ln(2), after deposition of each layer. Also, we use FEM and simulate the four-point probe by changing the probe spacing and configuration to discuss the possibility of measuring films thickness by four-point probe. The thesis discusses the assembling and design of NTU APPJ. We improve some defects of ITRI APPJ such as, exhaust system, moving stage and jet additional prats. We established a fabrication baseline using small area substrates, which will be used as a basis for further optimization of the parameters. By controlling the main gas, voltage and duty cycle, it comes out the best films properties. Also, we measured the thickness, Hall measurement, XRD and transmittance to find out the reasons of the low sheet resistance of samples in low main gas flow rate. At last, we conduct the large area deposition with the baseline parameters, and obtain an average sheet resistance of 62.8 Ω/□, average transmittance in visible region over 87%, and the uniformity 14%, for GZO thin films.
Subjects
multilayer thin films
finite element method
APPJ
four-point probe
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-105-R03522514-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):56b10a65703e2e37520189a5cca4b7c9