PhD Opportunities for 2013!


The project aims to uncover and harness new electronic properties of silicon nanodevices in which quantum mechanical effects play crucial roles.

Silicon lies at the very core of modern information and communication technology. This means that on one hand, the technology is highly developed and enables exquisite control over physics experiments at the nanoscale. On the other hand, new physical insights and device concepts can potentially have enormous impact through their applications.

In the nanoscience group at the University of Bath, we are investigating electronic properties of low-dimensional systems in silicon nanodevices aiming to uncover new physics of low-dimensional systems as well as furthering our understanding of the material properties of silicon itself.

There is scope for a number of projects depending on the strengths and interests of the candidates. Possibilities include the design and fabrication of new multilayer structures, manipulating the band-structure of silicon to investigating the fundamental physics of interactions between charge carriers. The projects will form part of on-going collaboration with scientists in France and Japan from both industry and academia.

Here are three examples.


If you place two current carrying wires close together in parallel one might expect that not a lot happens, except that the wires experience forces due to the resulting magnetic fields. The microscopic origin of electrical current is, however, the motion of charge carriers: electrons in this case. Electrons in each of the wires feel the net effect of the motion of electrons in the other wire through the net magnetic field. Effects due to the individual nature of electrons
somehow average out or are extremely small.

So what happens if you bring the wires so close together that electrons in one
wire can “see” the individual electrons in the other wire? How can you achieve
such conditions in practice? Will electrons in one wire “rub” against electrons in the other causing friction? What happens if we make the wires out of semiconductors and put valence band holes in one wire and conduction band
electrons in the other? Will the electrons and holes bind? If so, what properties
will these bound pairs have? What happens with quantum mechanics? Will there be new states of matter?

This project aims to produce experimental answers to these questions for charge carriers generated in nanostructures built using state-of –the-art silicon technology. It forms part of an ongoing project to explore new physical regimes using silicon technology, at the same time providing useful physical insights into these technologically vital silicon-based structures.


The interface between silicon and silicon dioxide is the basis on which much of modern information and communication technology is built. It is also the substrate or host material of choice for a wide range of scientific and technological investigations. Owing to its ubiquity, long history and importance in society, its basic properties are often assumed to be well understood. Recent experiments, however, have unexpectedly revealed that certain preparation conditions lead to a new type of interface at which the electronic properties are profoundly altered. These experiments show that an aspect of silicon band-structure known as “valley-splitting” can be enlarged well beyond an order of magnitude than had previously been possible, and that its magnitude can be tuned flexibly, in-situ, using standard electrical gates [PRL 96, 236801 (2006)]. The band-structure of a material lies at the very heart of the physics of any crystalline solid dictating all properties involving electrons such as how suitable the material is for use in a transistor and what colour of light the material absorbs and emits. As such, large alterations to valley-splitting can be expected to have far reaching consequences for a variety of physical properties. At present, however, we know little about this effect – what causes it and what consequences it has; the new interface is a new material with unknown properties.

This project aims to experimentally establish what causes this newly discovered giant valleysplitting effect and the consequences this has on electrical and optical properties. Since the valley-splitting is electrically tuneable, new properties discovered at large valley-splitting will also be electrically tuneable or switchable. Furthermore, this silicon–silicon dioxide material system is automatically compatible with the vast arsenal of cutting-edge silicon technology. Any new functionality can be embedded into silicon-based systems at the very deepest level of integration.


The vast range of applications semiconductor structures have found partly stems from our ability to tailor their physical properties. This is often achieved by creating a stack of thin layers of mono-crystalline semiconductors which enables the electronic band-structure to be engineered. These “heterostructures” are usually made by hetero-epitaxial techniques such as MBE (Molecular Beam Epitaxy) or MOVPE (Metal-Organic Vapour Phase Epitaxy). These techniques, however, are fundamentally limited as to the material combinations that can be embedded in a structure. This in turn limits what we can get the semiconductor structures to do.

However, there is an alternative method of making heterostructures, which is to use recently developed techniques of direct bonding and layer transfer. Direct bonding is a method of sticking two materials together in which two sufficiently flat and clean surfaces are initially held together by van der Waals forces and hydrogen bonds and then, thermally treated allowing the materials to fuse. In layer transfer, a layer of material prepared on a sacrificial substrate can be transferred onto another wafer by direct bonding, followed by the removal of
the sacrificial substrate.

The project will aim to create new structures that were impossible by hetero-epitaxial techniques by using direct bonding and layer transfer and to assess their physical properties. The goal is to create new devices with new functionalities, and new structures enabling new physical regimes to be accessed for fundamental physics experiments.


The project aims to create new electronic nano-devices with new physical properties, by controlling and exploiting self-assembling crystalline phases of biological liquid crystals.

By using nano-scale electrodes patterned onto a silicon chip, crystalline order of the bio-molecules can be induced exactly at the electrodes. The structure can then be used as a template for transferring the spatial structure to a material of choice by electrolytic-deposition. The electrochemically deposited structure will automatically be connected to the electrodes allowing electrical characteristics to be monitored during growth for in-situ feed-back control. With suitable geometry of the pre-patterned electrodes, the system would automatically form an electronic device enabling the properties of the superstructure to be characterised electrically, eliminating the need for device-processing-development usually required for new materials. 

Physically, the deposited structure constitutes a 3-dimensional superlattice with a periodically modulated potential or a 3-dimensional crystal of quantum dots depending on the dimensions and band properties of the deposited material. A new generation of materials with new electronic properties can thus be expected, as the band-structure, which dictates the electronic properties of any crystalline material, can be engineered in the third dimension.

The work will involve the use of the Nanofabrication facility and collaboration with materials scientists.


Applicants should have a background in the physical sciences and have or expect to gain a First or Upper Second Class UK Honours degree, or the equivalent from an overseas University. Possible funding sources include the Doctoral Training Account (for UK applicants) or Faculty/University studentships and scholarships. Applications from self-funded students are always welcome.

Please contact me by sending me an e-mail in the first instance.