Structural and optical properties of ZnCdS nanoflowers and nanocrystalline thin films grown by microwave – assisted chemical bath deposition

by Mazin
(Malaysia)

Original Text: Structural and optical properties of ZnCdS nanoflowers and nanocrystalline thin films grown by microwave – assisted chemical bath deposition.

1. Introduction
Fabrication of nanomaterials have lock onto a great interest in materials research over the past decade due to their unique chemical and physical properties.
Very high surface to volume ratio is the most basic attribute could lead to get new atomic arrangement and this will effect especially on the optical properties of nanomaterials1
Nanoparticles has optical properties different from bulk where the absorption and/or emission wavelength can be controlled by particles size and surface functionalization. Since more than two decades ago, II-VI semiconductors thin films have a wide attention from the scientific researches due to the various of its applications in solar cell and other optoelectronics devices[2. Among of the group II-VI binary compound, cadmium sulfide (CdS) and zinc sulfide are the most typical materials. CdS is n-type semiconductor with 2.42 eV direct energy gap at room temperature, thus it is widely use to fabricate solar cell with CdTe, Cu2S and CuInSe2. The energy gap of CdS is relatively low which lead to absorbs the blue portion of the solar spectrum from the window layer and this will cause a decrease in current density of solar cell 2, 3. Adding ZnS (Eg=3.66 eV) to CdS lead to increasing the energy gap from 2.42 to 3.66 eV dependent on Zn/Cd ratio4.
Cd1-xZnxS thin films were obtained using various techniques such as thermal evaporation 5, solution growth 6, spary pyrolysis 7, dip-coating 8 and chemical deposition9. Another technique uses the microwaves, which are electromagnetic radiation with frequencies ranging from 0.3–300 GHz. Since 1986, microwave irradiation has been broadly applied as a heating method in chemistry and material synthesis due to the direct interaction between the radiation and materials, resulting in very short reaction times, the production of small inorganic particles with narrow particle size distribution, and low energy consumption compared with conventional methods 10, 11. Microwave radiation first couples with the material and then the material absorbs it. Thus, the electromagnetic energy is transformed into thermal energy and the heat is created from inside the material, in contrast with conventional heating methods where heat flows inward 12. In the presence work, ZnxCd1-xS nanoflowers and nanocrystalline thin films were synthesis using microwave – assisted chemical bath deposition method and some physical properties of these films are studied.

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Revised Text:

1. Introduction

Fabrication of nanomaterials has become of great interest in materials research over the past decade, due to their unique chemical and physical properties.

The very high surface to volume ratio is the most basic attribute and could lead to new atomic arrangements which would especially effect the optical properties of nano-materials(1)

Nano-particles have optical properties different from larger particles, where the absorption and/or emission wavelengths can be controlled by particle size and surface functionalization. For more than two decades, II-VI semiconductor thin films have had widespread attention by scientific researchers due to the variety of their applications in solar cell and other opto-electronic devices(2).

Among the group II-VI binary compounds, cadmium sulfide (CdS) and zinc sulfide are the most typical materials. CdS is n-type semiconductor with 2.42 eV direct energy gap at room temperature, thus it is widely used to fabricate solar cell with CdTe, Cu2S and CuInSe2. The energy gap of CdS is relatively low which leads to the absorbtion of the blue portion of the solar spectrum from the window layer and this causes a decrease in current density of solar cells (2, 3). Adding ZnS (Eg=3.66 eV) to CdS leads to increasing the energy gap from 2.42 to 3.66 eV dependent on the Zn/Cd ratio(4).

Cd1-xZnxS thin films were obtained using various techniques, such as; thermal evaporation (5), solution growth (6), spary pyrolysis (7), dip-coating (8) and chemical deposition(9). Another technique uses microwaves, which are electromagnetic radiation with frequencies ranging from 0.3–300 GHz. Since 1986, microwave irradiation has been broadly applied as a heating method in chemistry and material synthesis, due to the direct interaction between the radiation and the materials, resulting in very short reaction times, the production of small inorganic particles with narrow particle size distribution, and low energy consumption compared to conventional methods (10, 11).

Microwave radiation first couples with the material and then the material absorbs it. Thus, the electromagnetic energy is transformed into thermal energy and heat is created from inside the materials, in contrast to conventional heating methods, where heat flows inward (12).

In the presence work, ZnxCd1-xS nano-flowers and nano-crystalline thin films were synthesized using a microwave assisted chemical bath deposition method and some physical properties of these films were studied.

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