Photoemission on narrow Bandgap II-VI-semiconductors
Diplomarbeit

HUMBOLDT-UNIVERSITÄT ZU BERLIN
INSTITUT FÜR PHYSIK
AG ELEKTRONISCHE EIGENSCHAFTEN UND SUPRALEITUNG

Matthias Kreier

Date: Berlin, 16. 7. 2007

Contents

• 1. Introduction
• 2. Fundamentals in angle-resolved photo emission spectroscopy
  • 2.1 Principle of measurement
  • 2.2 Photoemission and band structure
  
  
• 3. Experimental details
• 4. Experimental Method and Equipment
  • 4.1 Method and Principle
    • 4.1.1 Matching Highly Volatile Surfaces with UHV Electron Spectroscopy
    • 4.1.2 Liquid Jed: Formation, Theory and Characteristics
    • 4.1.3 Synchrotron Radiation and Insertion Devices
  • 4.2 Setup and Equipment
    • 4.2.1 Electron Spectrometer
    • 4.2.2 MBI Undulator Beamline at BESSY II
  
  
• 5. Sourface Mounted II-VI Semiconductors Band Diagramm
  • 5.1 Generic Results
  • 5.2 Wiggle in Band Structure Calculations
  • 5.3 GW-Approximation
  
  
• 6. Summary and Outlook
  • 6.1 Summary
  • 6.2 Outlook
  
  
• 7. Appendix
  • 7.1 ab initio Calculations on a supercluster
  • 7.2 Data Conversion in C++ and Java
  • 7.3 Publications
  
  
• Bibliography

1. Introduction

The crystals of HgTe and PbTe as well as CdTe and SnTe have been studied during the last tree decades very intensively. Whereas the first two are considered to be narrow bandgap semiconductors the latter two are semimetals. CdTe shows an inverted bulk bandstructure and has therefore a negative bandgap.

Here I describe in two sentences the content of each chapter[1]. At least one citation will be included.

Finally this chapter ends.

2. Fundamentals in angle-resolved photo emission spectroscopy

2.1 Principle of measurement

Well, it is very easy. Have a look at the following formulae:

$$E=mc^{2}$$

As you can see, the intensity not only depends on the wavefunction of the incomming light but due to the vector potential to the azimuth and polar angle. This is discovered by an spherical analysator (Scienta SES 100) with a multichannel plate.

$$\Delta E=1/2E_{PASS}+\alpha$$

This formulae is obtained by a single integration of all amplitude data measured within a certain period. Later recalculated intensity revitalises all dependencies.

Here follows a little text with no meaning, only to get to page .. next .. and there I need a little paragraph.

Maybe this is my paragraph, I hope I'll like him. Here now a picture is to be introduced. Let's see if it figures out.

2.2 Photoemission and band structure

While the photo emission is as easy and then later and here a text. I'll try to impact a formulae in this text with Lyx so let's see if it works: $2k_{B}T=25meV$ sollte mit Subs funktionieren. Probieren wir es gleich noch einmal.

$$E_{k}=\sin(\beta+\pi/4)$$

$\vec{E=1/2\sin a}$und so geht der Text weiter. ein $\vec{E}=\frac{1}{2}mv^{2}$und so geht die english translation further and further. Keep on thinking about it. Maybe it helps. See you tomorrow. As for me - I can't go on living like that and pretend that everything is ok. Therefore don't ask, just read.

As for the bandstructure one obtains various many-body-effects on the surface. Usually described as a thin layer, it is not nessesaryly a big deal. Watch this formulae:

$$E_{f} = E_{gap}+E_{Austrittsarbeit}+k_{b}T^{1/2}$$

Not linear dependant it perfectly shows nothing.

Fitting parameters are not avaliable. Suiting 4 Gauss profiles leed to an extraordinary dispersion in light intensity:

photon energy	kink at [eV]	\vec	transmission
22.12	3.546	12.1	14.3
22.12	6.543	12.4	35.3

The slight shift in intensity is connected to the thin bilayer splitting in HTSC based on YBCO. Bi2212 dosn't shows this behavior.

3. Experimental details

All measurements were taken with the SCIENTA SES 100 and the WESPHOA I at the laboratry in Adlershof, Newtonstr. 14. Very usefull for interpretration of the mesurement data was all GPL-software and so on.

4. Experimental Method and Equipment

4.1 Method and Principle

4.1.1 Matching Highly Volatile Surfaces with UHV Electron Spectroscopy

4.1.2 Liquid Jed: Formation, Theory and Characteristics

4.1.3 Synchrotron Radiation and Insertion Devices

4.2 Setup and Equipment

4.2.1 Electron Spectrometer

4.2.2 MBI Undulator Beamline at BESSY II

5. Sourface Mounted II-VI Semiconductors Band Diagramm

5.1 Generic Results

5.2 Wiggle in Band Structure Calculations

5.3 GW-Approximation

6. Summary and Outlook

6.1 Summary

6.2 Outlook

7. Appendix

7.1 ab initio Calculations on a supercluster

7.2 Data Conversion in C++ and Java

7.3 Publications

List of Figures

Bibliography

1

A. Fleszar, W. Hanke, Phys. Rev. B 71, 045207 (2005)

2

D. A. Shirley, Phys. Rev. B 5, 4709 (1972)

Acknowledgements

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Photoemission on narrow Bandgap II-VI-semiconductors
Diplomarbeit

HUMBOLDT-UNIVERSITÄT ZU BERLIN
INSTITUT FÜR PHYSIK
AG ELEKTRONISCHE EIGENSCHAFTEN UND SUPRALEITUNG

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