Structural and optical properties of MgxZn1-xO fabricaed by pid

مقدم أطروحة جامعية

Satmon, Jihan Admon

مشرف أطروحة جامعية

Haydar, Adawiya Jumah

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم العلوم التطبيقية

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2011

الملخص الإنجليزي

-For this thesis work, films have been grown under various deposition conditions in order to understand the effect of processing on the film properties and to specify the optimum condition, namely substrate at temperatures of (Room Temperature - 500°C), oxygen pressure (10-2, 10-1 , 2×10-1) mbar, laser fluence 1.6 J/cm2 , and with different Mg contents (x= 0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1), using double frequency Q-switching Nd:YAG laser beam (wavelength 532nm), repetition rate (1 - 6) Hz and the pulse duration of (10 ns), to deposit MgxZn1-xO films on sapphire and glass substrates with thickness of about 250±50 nm for all MgxZn1-xO films at different deposition condition and the number of laser pulses was 100 pulses.

The quality of the Mg0.2Zn0.8O films (for x= 0.2) deposited on sapphire substrate is improved with increasing the substrate temperature from RT to 500оC, from X-ray diffraction patterns (XRD), the full width at half maximum (FWHM) of the (0002) peaks of these films decreases and the largest grain size (55.6791nm) obtained as the substrate temperature increases to 500оC, while the calculated optical band gap of the Mg0.2Zn0.8O films increases to 4.3 eV at 500оC.

When the Mg0.2Zn0.8O film is grown at 300оC on sapphire substrate with a smallest grain size (19.7037nm) compared to the film deposited on glass substrate (38.1577nm).

This indicates the superior crystallinity of the film which also has observed from the AFM images.The optical results show that the transmission of the MgxZn1-xO films are greater than 85% in the visible spectrum range which increases with the increasing of substrate temperature and Mg content.

The absorption can be extended to lower wavelength range with higher magnesium contents, which can improve the transparency in the ultraviolet region.

The band gap energy of MgxZn1-xO thin films deposited on sapphire substrate was found to be changed to the higher energy side with increasing of Mg concentrations.

By changing Mg content from x=0 to x=1, the optical band gap of MgxZn1-xO alloy films can be tuned from 3.4 eV to 5.9 eV, while the refractive index decreases from (1.96 – 1.75) as Mg-content increases from (0 to 1) at 400nm wavelength.

This provides an excellent opportunity for bandgap engineering for optoelectronic applications.

The MgxZn1-xO films are of high single crystalline quality by changing Mg content from x=0 to x=1, with hexagonal wurtzite structure for x ≤ 0.3, changed to cubic structure for 0.6≤ x ≤ 1 and mixed phase was observed for x=0.4.

The effect of O2 background pressure on the structure, crystallinity orientation and optical properties of the Mg0.2Zn0.8O film have also been studied.

A small grain size 4.3594nm and smoother surface at low O2 pressure than that at high O2 pressure.

In addition, the photoluminescence (PL) results for MgxZn1-xO films indicate that the stronge UV peak was found at (333.27nm) from Mg0.2Zn0.8O film (for x=0.2) grown on sapphire substrate.

While for ZnO film (for x=0) the UV peak was found at (367.78nm) with broad band in visible region (534.67nm) was also observed.

Z-scan technique was used to study the nonlinear optical properties, represented by the nonlinear refractive index and nonlinear absorption coefficients of ZnO, Mg0.2Zn0.8O and MgO thin films.

Z-scan experiment was performed, using a double frequency Q-switching Nd:YAG laser pulses at two different aperatures (opened and closed).

The results show that the nonlinear refractive index directly proportional to the input energy.

Also we found that the MgO film in our experiment has weak nonlinear optical response at 532nm, and the high nonlinear optical properties observed here result from the ZnO and Mg0.2Zn0.8O films.

التخصصات الرئيسية

الفيزياء

الموضوعات

• الخواص الميكانيكية
• الخواص الضوئية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-304928