software to fit optical spectra - Quantum Materials Group

Contents
1. Introduction ....................................................................................................... 4
1.1. Foreword ...................................................................................................................... 4
1.2. What is RefFIT for? ..................................................................................................... 5
1.3. About this manual ........................................................................................................ 6
1.4. Let’s keep in touch ....................................................................................................... 7
2. Basics of optical data fitting.............................................................................. 8
2.1. Non-linear modeling..................................................................................................... 8
2.1.1. Levenberg-Marquardt algorithm ......................................................................9
2.1.2. Simultaneous fitting of several datasets of different types.............................12
2.1.3. Confidence limits............................................................................................13
2.2. Modeling of the dielectric functions .......................................................................... 14
2.2.1. Physical properties of the dielectric functions................................................14
2.2.2. Why modeling? ..............................................................................................15
2.2.3. Formula-defined dielectric functions .............................................................16
2.2.4. Variational (free-shape) dielectric functions (KK-constrained).....................17
2.2.5. ‘Not-KK-constrained’ variational dielectric functions...................................22
2.3. Differential modeling ................................................................................................. 23
3. Tutorial ............................................................................................................ 25
3.1. Drude-Lorentz fitting of a reflectivity spectrum ........................................................ 25
3.2. Simultaneous fitting of several data types.................................................................. 36
3.3. Using macros.............................................................................................................. 42
3.3.1. Writing a simple macro ..................................................................................42
3.3.2. Using cycles in a macro: the temperature dependence of phonon spectra .....44
4. Reference......................................................................................................... 51
4.1. System requirements .................................................................................................. 51
4.2. Installation and starting RefFIT ................................................................................. 51
4.3. Parameters .................................................................................................................. 52
4.4. Experimental Parameters............................................................................................ 53
4.5. Models........................................................................................................................ 54
4.5.1. Saving and loading models.............................................................................54
4.5.2. Editing models................................................................................................55
4.5.3. Model types ....................................................................................................55
4.6. “Dielectric function” model ....................................................................................... 56
4.6.1. Drude-Lorentz dielectric function ..................................................................59
4.6.2. Special dielectric functions.............................................................................59
4.6.3. Variational (free-shape) dielectric function....................................................62
4.7. Special models............................................................................................................ 63
4.7.1. Differential dielectric function .......................................................................64
4.7.2. Reflection and transmission of a multi-layer sample .....................................64
4.7.3. Ellipsometry of an orthorhombic sample .......................................................66
4.7.4. Differential ellipsometry of an orthorhombic sample ....................................68
4.7.5. Ellipsometry of an orthorhombic film on an orthorhombic substrate ............68
4.7.6. Extended Drude ..............................................................................................70
Guide to RefFIT Page 2