Synthesis and characteristic study of nanostructured (PbS n-Si)‎ by chemical bath deposition

Dissertant

Kazim, Suad Mahmud

Thesis advisor

al-Jawad, Salma M. H.
al-Zuhayri, Ali M. M.

University

University of Technology

Faculty

-

Department

Applied Sciences Department

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

In this work nano PbS films were prepared using chemical bath deposition technique, which is a simple, inexpensive and suitable technique for large deposition area.

Lead acetate salt was used as a source of lead ions and thiourea as a source of sulfide ions.

During deposition several growth parameters have been considered in this work to specify the optimum conditions, namely (deposition time, temperature of path solution, pH value, lead ion concentration and thiourea ion concentration).The structure, optical and electrical properties of nano PbS films were investigated and analyzed extensively for a variety of growth conditions.

The structural characteristic of the films prepared on a glass substrates have studied using X-ray diffraction, results shows that all the films were polycrystalline cubic structure for all deposited films under different growth conditions.

The electrical properties of these films were studied.

The d.c conductivity for the deposited films increases from 4.1*10-6 to1.5*10-5(.cm)-1 with thickness increases.

From study of the electrical conductivity with temperature the films shows two activation energies Ea1 and Ea2 which are decrease from 0.567 to 0.351 eV and from 0.302 to 0.119 eV with thickness increases.

Hall measurements showed that all the films are p-type and carrier concentration increase from (4.4 3 * 1015 to 2.5* 1016) cm-3 with thickness increase.

Also we observed that the mobility were decreases with increasing of thickness.

Optical measurements (transmission and absorption) were carried out.

Transmittance decreased with increasing the deposition time, temperature of solution and pH value, while the transmittance increased with increasing lead ion concentration.The direct optical energy band gap range was between (1.68 -2.4) eV.

Nano crystalline PbS was deposited on the n- type silicon to study and characterize the heterojunction.

The I-V characteristics of the PbS/n-Si heterojunction have been studied,where the current-voltage characterization under dark conditions shows that forward bias current variation exponentially with voltage bias.

Under illumination, the photocurrent density decreases with increase of deposition time.

The reverse bias capacitance for PbS/n –Si heterojunciton was measured as a function of bias voltage at the frequency 200 KHz, and it is indicated that these heterojunction are abrupted.

The capacitance decreases with increasing the reverse bias voltage.

High spectral responsivity of 0.44 A/W, quantum efficiency 80% , and specific detectivity 1.98 * 1011 cm Hz1/2 W-1 where obtained.

Also the shape of the spectrum of nano PbS/n -Si is extended into the blue region, due to widening of the window band gap.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

Topics

• Nanotechnology

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-418453