## Electronic Theses and Dissertations

1-1-2010

Dissertation

Ph.D.

#### Department

Physics and Astronomy

Barry L. Zink

#### Keywords

amorphous silicon alloys, e beam lithography, silicon nitride, thermal conductivity, thermoelectrics, Thin films

#### Abstract

It is important to understand thermal transport behavior in materials for

technological and fundamental physics applications. Many efforts have been made in the past for explaining thermal conduction in solids.

It has been observed that thermal transport properties may change with reducing size of the sample, especially as sample size approaches the nanoscale regime. The deviation in these properties, mainly in thermal conductivity, may change the choice of the material for different applications such as thermoelectricity. Thermoelectric materials are a possible source of sustainable energy and can play an important role in the fight against the present energy crisis. Recently, better thermoelectric materials have become available in bulk form as compared to thin film form, with higher figure of merit ($ZT={\alpha}^2 \sigma{T}/\textit{k}$).

ZT is a dimensionless quantity which is used to characterize the performance of thermoelectric materials in terms of the efficiency.

Figure of merit (ZT) depends on three fundamental properties including thermal conductivity (\textit{k}) which is challenging to measure for thin films. This is due to several reasons such as large or more than one background contribution and radiation heating above 100 K.

Precise measurements of thermopower (${\alpha}$) also become critical for thin films in order to calculate ZT and the efficiency.

For devices which rely on thin film technology it is important to have an accurate knowledge of how a material behaves as a thin film in a wide range of temperature. All three of these properties are a function of charge carrier concentration as well as of temperature.

In my thesis, I will present novel experimental techniques and measurements of thermoelectric properties in amorphous based thin films over a wide range of temperature. Amorphous Si alloys are expected to have high efficiency for thermoelectric purposes

because of their low thermal conductivity and the fact that we can control the charge carrier concentration for optimized thermopower($\alpha$) and electrical conductivity($\sigma$) by controlling the dopant concentration. Thermal properties of pure amorphous thin films are also potentially useful in micro- or nano fabrication techniques

such as electrically insulating integrated devices.

#### Provenance

Recieved from ProQuest

Rubina Sultan

166 p.

application/pdf

en

#### Discipline

Condensed matter physics

COinS