Engineering International

Alamgir Kabir ¹, Rumelia Murshed ¹, Ummul Husnaeen ¹, Zahid Hasan Mahmood ¹

Affiliations
1 Dept. of Applied Physics, Electronics & Communication Engineering, Dhaka University, BD

Abstract

Electronic devices and integrated systems are reduced to the size of micron and nanometer level and it becomes particularly important to predict the thermal transport properties of the components. Because of a unique structure and novel properties of carbon nanotubes (CNTs) have attracted significant attention. In this article, thermal transport properties of single wall CNTs (SWCNTs) are introduced. Combining equilibrium and nonequilibrium molecular dynamics with carbon potentials, we have studied the thermal conductivity of carbon nanotubes and its dependence on temperature. Phonon conduction depends on band gaps as well as thermal contact resistance of metallic CNTs, governed by phonon scattering and it shows evidence of 1-D quantization of the phonon band structure. We have studied here the thermal conductivity of single wall nanotubes dependence on chirality structure, dimensions of tubes, defects and vacancies in tubes. We found that the single wall carbon nanotubes have very high thermal conductivity comparable to diamond crystal and in-plane graphite sheet.

Keywords

Thermal Transport, Phonon, Green-Kubo Method, Quantization, Umklapp Scattering, Wiedemann-Franz Law

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Nahid Akter ¹, Abul Hossion ¹, Mahbubul Hoq ², Sardar Masud Rana ², AnzanUz Zaman ², Nasrul Haque Mia ², Alamgir Kabir ¹, Zahid Hasan Mahmood ¹

Affiliations
1 Applied Physics, Electronics and Communication Engineering, Dhaka University, BD
2 Institute of Electronics, Atomic Energy Research Establishment (AERE), Dhaka, BD

Abstract

The parameters of crystalline semiconductor such as types of semiconductor, uniformity of impurity concentration of doped wafer, majority charge carrier concentration, sheet resistivity of doped wafer surface play an important role in solar cell fabrication process during emitter diffusion, that is the most critical step. In this paper, we have used a low cost in house made hot probe measurement setup. A hot plate was used to heat up the wafer up to 100°C. Two k-type thermocouples were placed simultaneously in contact with the hot and cold surface of the wafer to measure the temperature in situ for both hot and cold probe. We have used two copper probes with a voltmeter connected to measure the potential difference (thermoelectric voltage) between two probes for various temperatures up to 100°C with an interval of 10°C. We have taken measurement for commercial silicon wafer (thickness 200 μm) and one side polished 4 inch diameter Si wafer (thickness 660 μm) to determine the wafer type (n-type or p-type). We also calculated thermopower or Seebeck coefficient from the voltage vs. time curve, that is constant for particular substrate. As a process monitoring tool for solar cell fabrication process, after n-type diffusion using POCl3 on p-type silicon wafer of thickness 200 μm, we have done wafer mapping that gives us the information of doping uniformity over the whole surface of wafer both front and back side

Keywords

Hot Probe, Seebeck Effect, Thermal Conductivity, Wafer Mapping

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