Design and construction of low-pressure D. C.-sputtering plasma system for preparing gas sensors

Other Title(s)

تصميم و بناء منظومة الكاثود المتوهج في بلازما الضغط الواطئ و الترذيذ المستمر لتحضير متحسس غازي

Dissertant

Ibrahim, Fuad Tariq

Thesis advisor

Khalaf, Muhammad Khammas
al-Tamimi, Nadhirah Abbas Ali

Comitee Members

al-Hayif, Abd al-Husayn K.
al-Kazimi, Mahasin F. Hadi
Muhammad, Ghusun Hamid
Twij, Wisam Abd Ali

University

University of Baghdad

Faculty

College of Science

Department

Department of Physics

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

In this work, a DC planar sputtering system has been successfully designed and fabricated.

The glow discharge plasma chamber was made of stainless steel with a length of 35 cm and a diameter of 31 cm.

This chamber consists of two stainless steel planar sputtering electrodes used as anode and cathode each of diameter of 10cm.

Electrical plasma properties have been studied via studying the currentvoltage, current-pressure, and Paschen curves.

The electrical plasma properties were studied at different inter-electrodes spacing, gas pressure, and argonoxygen mixture.

The adopted inter-electrodes spacing was 5cm.

We choose the left side from the Paschen minimum to study plasma parameters and to prepare the SnO2 thin films.

The best argon-oxygen mixture obeys this condition (Ar/O2=1/2).

The plasma parameters like electron temperature Te, electrons density ne, ions density ni, plasma potential VP and floating potential VF , were measured using single Langmuir probe with different gas pressures, and argon-oxygen mixture.

It is found that the electron temperature decreases and electron density increased with increasing the argon gas pressure and increasing the oxygen to argon mixed flow.

Three group of SnO2 thin films deposited using dc-plasma sputtering system on glass substrate with rate of deposition time 60min.

The first group was deposited with different discharge current (10, 15, 20, and 25mA).

The second group prepared at different gas pressure (0.15, 0.05, 0.035, and 0.015mbar).

The third group deposit with varying argon to oxygen mixed flow.

The structures of the films prepared on glass substrate were examined by X-ray diffraction analysis.

The results show that the structure is polycrystalline with tetragonal structure and preferential orientation in the (110), and(101) directions.

The increasing discharge current and decreased gas pressure enhance SnO2 thin films crystallite structure.

The optical measurements showed that the sputtered SnO2 films have direct energy gap (Eg) (4eV decreases to 3.92eV) with decreasing of gas pressure, and increased from 3.25eV to 3.97eV with increasing of oxygen flow respect to argon flow.

The surface morphology of SnO2 thin films have been studied by using Atomic Force Microscope and Scanning Electron Microscope .

The nano grain size value depended on discharge current, gas pressure, and Argon- Oxygen mixture flow.

The nano grain size value increased with increasing discharge current and gas pressure, and decreased with increasing Oxygen- Argon mixture flow.

The surface roughness increased with decreasing grain size .

The sensitivity of SnO2 samples to NO2 gas in air ambient has been measured in gas sensing system.

All samples were tested at mixed ratio (1%, 2%, and 3% NO2: air) and bias voltage (6 volt).

The optimal operating temperature is found to be 220oC for SnO2 samples.

The maximum sensitivity is (57%) with fast response time (2.7s) and recovery time of (7.2s).

Main Subjects

Physics

No. of Pages

125

Table of Contents

• APA
• MLA
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Language

English

Data Type

Arab Theses

Record ID

BIM-607696