• thermal lithography
• AFM
• SThM
• Ucl

The aim of this thesis is to design a Scanning Thermal Force Microscope (SThM). This machine manufactures nano devices made with polymers utilizing a thermal process.
The process consists of heating up a thermal scanning probe by controlling the current flowing in it.
The first chapter of this thesis describes in general terms what an Atomic Force Microscope (AFM) is and what its functions are.
Afterwards there is an explanation of how an AFM can be developed in order to be used as an SThM.
The second chapter focuses on the features of the system we developed.
In this section, the description of the system is divided into four parts : the optics, the signal processing, the piezo controller and the thermal control.
In each of these parts, there is a brief description of its main features and the design choices we made.
The third chapter describes the optics of the system we developed following Binnig, Quate and Gerber’s 1986 design of the AFM.
This section also contains the results we obtained testing different lasers and the problems we had with the calibration of the system due to the thermal scanning probe used.
The fourth chapter deals with the signal processing of the system. Firstly, there is an analysis of the noise that affects the system. The value of the signal-noise ratio is obtained from experimental data gathered doing scans of a step with a height of 30 nm. Afterwards there is a description of the development of a filter we made in order to reduce the noise affecting the system.
The fifth chapter describes the development of the thermal control of the system. The control of the temperature is obtained through a Wheatstone bridge and a proportional-integral-differential (PID) control.
We developed the system using a digital signal processor (DSP), a nano position controller, a 3A class red laser and a Butterworth low-pass filter which we designed and tested.
We decided to design the filter using Orcad and Multisim CAD programmes. The results obtained were processed through Matlab scripts. The control of the system requires the programming of the DSP which we programmed using AdWin language.
The main results achieved are : succeeding in scanning devices with a height of 30 nm and controlling the temperature of the system up to 220°Celsius.
This project has been developed in the Physics and Astronomy Department of University College London and is the property of Prof. Franco Cacialli and his group.