Deposition Of Nickel Selenide (Nise) By Chemical Bath Method

Description

ABSTRACT

Nickel selenide thin films have been deposited using chemical bath method on non-conducting glass substrates in a tartarate bath containing nickel sulphate octahydrate, hydrazine hydrate, sodium selenosulphate in an aqueous alkaline medium. The grown films were uniform, well adherent and black in color. The nickel selenide thin film revealed polycrystalline nature with hexagonal system. The direct optical band gap of the film was found to be 1.61 eV. Electrical resistivity of film was observed in the order of 103 (Ω cm) with p-type conduction mechanism

CHAPTER ONE

1.1                                                        INTRODUCTION

Among the materials of great interest are polycrystalline metal chalcogenides. Thin film materials with semiconducting, metallic, insulating or optical properties are in use in industry, medical science and technology, etc. Transition metal chalcogenides have received considerable attention because of their tunable properties. These materials, in thin film form, are often important candidates for photovoltaic conversion. This is due to matchable band gap with solar spectrum, high optical absorption band gap, and better electrical conductivity [1–11]. Similarly it shows interesting electric and magnetic properties. Polycrystalline electrodes are economically desirable for solar cell applications, where large area substrates are necessary. Hence, this study has been directed towards obtaining nickel selenide in the thin film form by chemical bath deposition method. The usual preparatory techniques are chemical vapour deposition, electrodeposition, spray pyrolysis, sputtering and chemical bath deposition. The chemical bath deposition offers several advantages of economy, conveniency and large area deposition capability [2–4,12]. Numbers of attempts have been made for the deposition of chalcogenide thin films such as CdS, CdSe, PbSe, HgSe, SnSe, Bi2Se3,Bi 2S3, and CoSe using chemical bath deposition method.

Few attempts have been made for investigation of NiSe using chemical bath deposition method. This paper describes the deposition of NiSe thin films by chemical bath deposition at room temperature. The preparative parameters such as growth rate, deposition temperature and the structural, compositional, morphological, optical, electrical properties were studied.

1.2                                               OBJECTIVE OF THE STUDY

Thin films of nickel sulphide were deposited from aqueous baths on indium tin oxide glass substrate. The chemical bath contained nickel sulphate, sodium thiosulfate and triethanolamine solutions. The aim of the present study was to analyze the different experimental conditions to prepare NiSe using chemical bath deposition technique.

1.3                                                   SCOPE OF THE STUDY

In this work, NiSe (nickel selenide) were deposited at different concentrations (0.10-1.00 M) using the chemical bath deposition technique. The other deposition variables were kept constant. The films were characterized using optical spectroscopy to investigate the absorbance, transmittance and reflectance versus wavelength measurements.

1.4                                           SIGNIFICANCE OF THE STUDY

Chemical solution methods such as hydrothermal, solvothermal, and chemical bath deposition (CBD) generally require lower temperatures for successful generation of quality films [5].  One of the earliest reports of the use of CBD was in the preparation of lead sulfide and lead selenide thin films for use as photoconductive detectors during World War II [5, 6]. Since then, CBD has become an attractive method due to its suitability for large scale deposition and the ability to deposit onto polymer substrates. It is characterised by simple formulation, ease of set up and low temperature requirements.

1.5                                            ADVANTAGES OF THE STUDY

The major advantage of CBD (Chemical bath deposition) in deposition of nickel selenide is that it requires in its simplest form only solution containers and substrate mounting devices. Chemical bath deposition yields stable, adherent, uniform and hard films with good reproducibility by a relatively simple process. The growth of thin films strongly depends on growth conditions, such as duration of deposition, composition and temperature of the solution, and topographical and chemical nature of the substrate.

1.6                                             LIMITATION OF THE STUDY

One major drawback of this method is the wastage of solution after every deposition.