Production of porous silicon by laser-induced etching

Dissertant

Jan, Sama Sami

University

University of Technology

Faculty

-

Department

Applied Sciences Department

University Country

Iraq

Degree

Master

Degree Date

2006

English Abstract

Porous silicon is produced in this work by photochemical etching of a n-type silicon wafer in hydrofluoric acid through laser-induced etching process.

Photosynthesization of the porous layer has been carried out under four different conditions, these conditions include; laser power density, the irradiation time, the etchant concentration and finally, the laser wavelength.

Five laser sources were used to prepare porous silicon layers.

Thus, different porous silicon structures were obtained in our experiments including pore-like structure (sponge-like structure) consisting of various nanocrystallites sizes.

Laser sources employed for photosynthesization of PS consist of a He-iNe laser source of 1.95 eV photon energy and an output power of 5 mW.

A diode laser of an output power of 2 W and a photon energy of 1.53 eV and three diode lasers of 1.89 eV? 1.91 eV and 2.54 eV photon energies with an identical output power of 5 mW.

It is found that the etching under nearly resonance condition produces the thickest porous layer of nearly 40 urn.

Therefore, the most efficient laser source was the diode laser of 1.53 eV.

Surface studies conducted in this work involve Surface morphology studies and the surface area measurements.

A large surface area within the porous layer of nearly 0.3-0.8 m2/cm3 was obtained.

The etching rate studies was found to increase drastically with increasing the laser wavelength, power density and was found to have its maximum value with HF concentration of 35 wt%.

The measured depths of porous We have also investigated the photoluminescence emission of the laser-produced porous silicon.

The photoluminescence spectra were obtained by an excitation source with a photon energy of 2.54 eV applied on the PS spot.

Our experimental data were analyzed and compared with the theoretical employed confinement model.

The confinement of an electron was proposed involving a Gaussian distribution of nanocrystallite sizes of porous silicon has been used to explain the experimentally observed photoluminescence spectra.

This model estimates the mean nanocrystallite sizes and the size distribution for the nanocrystallites present in the porous silicon layer, which contribute to the photoluminescence emission band.

Single-peak photoluminescence spectra were observed in this work which indicate the formation of single porous silicon layer.

Main Subjects

Physics

Topics

• Physics
• Silicon
• Semiconductors
• Lasers

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305449