Heterostructure by laser ablation of graphite

Dissertant

Muhsin, Mayyada Ahmad

Thesis advisor

Khashan, Khawlah S.

University

University of Technology

Faculty

-

Department

Applied Sciences Department

University Country

Iraq

Degree

Master

Degree Date

2013

English Abstract

In this work a suspension of carbon nanoparticles (polyyne, monocyanopolyynes and carbon nitride + carbon nanotube) was prepared by laser ablation using different solutions, and then sprayed on p-Si substrate.

FTIR spectra exhibit the presence of C≡C, C═C, C-C bond which indicates the formation of carbon nanoparticles and C-N, C═N, C≡N which suggests the formation of C3N4 crystalline.

UV absorption peaks coincide with the electronic transitions corresponding to linear hydrogen – capped polyyne (Cn+1H2), and represented a key or precursor to formation carbon nanotube.

The peak intensities increased when polyynes produced in different laser energies, the formation rates of polyynes increased with increased number of laser pulses, and these peaks disappeared with increasing the irradiation time.

While all suspensions exhibit a high absorption in UV region, and the band gap of carbon nanoparticles suspensions is change from (3.9-4 eV) at ethanol solution, from (3.9 to 4eV) at Iso-propanol solution, from (3.9 to 4eV) at deionize-water and from (3.9-4 eV) at ammonia solution, which changes as a function of laser energy, laser pulse and irradiation time.

The initial diameters of the CNPs particles are found to be approximately (1.2 to105.9 nm) in ethanol solution, (1.7 to 41.6 nm) in Iso-propanol solution, (9.4 to 70.5 nm) in deionize-water, and (4 to 83.3 nm) in ammonia solution.

The structures of carbon nanotubes (CNTs) obtained from this method observed few in ethanol (of 141.6 nm in length and 16.6 nm diameter), but high-quality of CNTs in Iso-propanol (with 11.1–46.15 nm in diameter and a (261.1- 592.3 nm) in length) and the CNTs are uniform diameters in deionize water (with diameters (12.2-25 nm) and a (500 - 708.3 nm) in length.

High performance rectifying contacts are obtained by depositing thin transparent carbon nanoparticles suspension on p type- silicon.

The ideality factor of both devices, which was found to be (2.76) for (CNPs/p-Si) and (1.93) for (CN/p-Si) heterojunction device, with high photoresponsivety of 0.33 A/W at 500nm and 2.33 A/W at 600nm for heterostructures CNPs/p- Si and CN/p-Si, respectively, where CNPs and CN prepared in ethanol and ammonia solution.

The corresponding quantum efficiency was 82.1 % and 481.6 % and specific detectivity was about 1.3x1019 cm Hz 1/2 W-1 and 1.2x1010cm Hz 1/2 W-1 for both devices.

Main Subjects

Physics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-418108