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日
期：2010.11.21
指導老師：林克默 博士
學
生：陳冠廷
Outline
1. Introduction
2. Experimental
3. Results and discussion
4. Conclusions
1.Introduction
• Recently pure and doped zinc oxide films have been
rediscovered as a subject of considerable interest in research
due to their physical properties and a wide range of possible
applications.
• In the sol–gel process, oxide thin films are obtained by post
deposition crystallization. As-deposited films must be
transformed into crystalline states from amorphous states by
post annealing.
• There are many factors affecting the crystallization behavior
of the films such as substrates used, heat treatment
conditions, organic compounds involved etc. This paper
addresses the effect of dopant on the microstructure, surface
morphology and the optical properties of ZnO thin films.
2.Experimental
• 2-Methoxy ethanol and monoethanolamine were used as the
solvent and stabilizing agent, respectively. The dopant source
for aluminium was aluminium chloride.
• The concentration of zinc acetate was 0.5 mol/l and the molar
ratio of monoethanolamine to zinc acetate was kept as 1:1.
• The solution was stirred for 1 h at 333 K to yield a clear
homogeneous and transparent solution using a magnetic
stirrer, which served as the coating solution.
• The solution was dropped ontoc-sapphire substrates.The
substrates were cleaned using trichloroethylene, methanol
and acetone and then rinsed with distilled water before the
deposition of the films.
3.Results and discussion
Fig. 1. XRD pattern of the pure and Al doped ZnO thin films.
• This indicates that dopant incorporation deteriorates the
crystallinity of films, which may be due to the formation of
stresses by ion size difference between zinc and dopant and
the segregation of dopants in grain boundaries.
Fig. 2. EDX spectrum of the ZnO films (a) pure and (b) Aluminium
doped.
• The energy dispersive X-ray spectra in Fig. 2 shows the peaks
associated with Zn and O atoms in the pure ZnO thin films and
the doped ZnO thin films shows the samples are free of any
impurities.
Fig. 3. SEM images of (a) pure and (b) Al doped ZnO thin
films.
• It is interesting to note that the grain sizes observed from SEM
is different from the grain size determined by using XRD.
• This shows the grains seen in the SEM are the domains
formed by aggregation of nanosize crystallites .
Fig. 4. (a) and (b) Cathodoluminescence spectrum of the pure and
Al doped ZnO film.
• According to quantum confinement theory, the energy band
gap of a semiconductor depends on the crystal size; its value
will increase with a decrease in crystal size.
• In most of the cases quantum confinement effects are
observed when the particle size decreases from 61 nm to 20
nm .
• In our case, the crystal size of pure ZnO films and Al doped
ZnO film are found to be 22 and 16 nm, respectively.
• Therefore the blue shift observed in UV excitonic emission for
Al doped ZnO film is probably caused by the quantum
confinement effect due to the decrease in the crystal size.
• The band gap widens with increasing Al content and upto 4
wt% of Al dopant .
4.Conclusions
•
氧化鋅薄膜已成功地在藍寶石基板上製備溶膠凝膠旋轉
塗佈過程中使用醋酸鋅為材料源。
• 純氧化鋅薄膜形態在Al摻雜改變為分離的球形結晶而六角
纖鋅礦結構沒有被摻雜物更改。
• ZnO薄膜的陰極發光分析表明紫外線激子放射在382nm附近，
深能階放射在490nm附近的可見光區。鋁的結合使紫外激
子放射和深能接放射轉移到短波長。
Thank you for your attention