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Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry.

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Presentation on theme: "Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry."— Presentation transcript:

1 Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Common epilayer defects

2 Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Common epilayer defects Investigate using rocking curves Common epilayer defects Investigate using rocking curves

3 Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Thin films (see Bowen & Tanner, High Resolution X-ray Diffractometry and Topography, Chap. 3) Common epilayer defects Investigate using rocking curves Layer & substrate peaks split rotation invariant Common epilayer defects Investigate using rocking curves Layer & substrate peaks split rotation invariant

4 Thin films Common epilayer defects Investigate using rocking curves Layer & substrate peaks split varies w/rotation Common epilayer defects Investigate using rocking curves Layer & substrate peaks split varies w/rotation

5 Thin films Common epilayer defects Investigate using rocking curves Broadens layer peak invariant w/ beam size peak position invariant w/ sample position Common epilayer defects Investigate using rocking curves Broadens layer peak invariant w/ beam size peak position invariant w/ sample position

6 Thin films Common epilayer defects Investigate using rocking curves Broadens layer peak may increase w/ beam size peak position invariant w/ sample position Common epilayer defects Investigate using rocking curves Broadens layer peak may increase w/ beam size peak position invariant w/ sample position

7 Thin films Common epilayer defects Investigate using rocking curves Broadens layer peak increases w/ beam size peak position varies w/ sample position Common epilayer defects Investigate using rocking curves Broadens layer peak increases w/ beam size peak position varies w/ sample position

8 Thin films Common epilayer defects Investigate using rocking curves Layer & substrate peaks split splitting different for symmetric & asymmetric reflections Common epilayer defects Investigate using rocking curves Layer & substrate peaks split splitting different for symmetric & asymmetric reflections

9 Thin films Common epilayer defects Investigate using rocking curves Various effects vary w/ sample position Common epilayer defects Investigate using rocking curves Various effects vary w/ sample position

10 Thin films Investigate using rocking curves Film thickness Integrated intensity changes increases w/ thickness Interference fringes Investigate using rocking curves Film thickness Integrated intensity changes increases w/ thickness Interference fringes

11 Thin films Mismatch constrained relaxed

12 Thin films Mismatch Layer & substrate peaks split – rotation invariant Measure, say, (004) peak separation, from which d/d = – cot = m* (mismatch) Mismatch Layer & substrate peaks split – rotation invariant Measure, say, (004) peak separation, from which d/d = – cot = m* (mismatch) constrained relaxed

13 Thin films Misorientation First, determine orientation of substrate rotate to bring plane normal into counter plane do scans at this position and at + 180° orientation angle = 1/2 difference in two angles Misorientation First, determine orientation of substrate rotate to bring plane normal into counter plane do scans at this position and at + 180° orientation angle = 1/2 difference in two angles = 90°

14 Thin films Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans = 90° shift +

15 Thin films Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans = 90° shift –

16 Thin films Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans = 90° no shift

17 Thin films Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans Misorientation First, determine orientation of substrate Layer tilt (assume small) layer peak shifts w/ in scans = 90° no shift

18 Thin films Dislocations From: high mismatch strain, locally relaxed local plastic deformation due to strain growth dislocations Dislocations From: high mismatch strain, locally relaxed local plastic deformation due to strain growth dislocations

19 Thin films Dislocations From: high mismatch strain, locally relaxed local plastic deformation due to strain growth dislocations Estimate dislocation density from broadening (radians) & Burgers vector b (cm): = 2 /9b 2 Dislocations From: high mismatch strain, locally relaxed local plastic deformation due to strain growth dislocations Estimate dislocation density from broadening (radians) & Burgers vector b (cm): = 2 /9b 2

20 Thin films Curvature R = radius of curvature, s = beam diameter angular broadening = s/R = beam radius broadening 5 mm 100 m 10" Curvature R = radius of curvature, s = beam diameter angular broadening = s/R = beam radius broadening 5 mm 100 m 10"

21 Thin films Relaxation Need to measure misfit parallel to interface Both mismatch & misorientation change on relaxation Interplanar spacings change with mismatch distortion & relaxation – changes splittings Relaxation Need to measure misfit parallel to interface Both mismatch & misorientation change on relaxation Interplanar spacings change with mismatch distortion & relaxation – changes splittings

22 Thin films Relaxation Need to measure misfit parallel to interface Both mismatch & misorientation change on relaxation So, also need misfit perpendicular to interface Then, % relaxation is Relaxation Need to measure misfit parallel to interface Both mismatch & misorientation change on relaxation So, also need misfit perpendicular to interface Then, % relaxation is

23 Thin films Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen reflecting plane

24 Thin films Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen

25 Thin films Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen Relaxation Grazing incidence Incidence angle usually very low….~1-2° Limits penetration of specimen Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen

26 Thin films Relaxation Grazing incidence Incidence angle usually very low….~1-2° Reflection not from planes parallel to specimen surface Relaxation Grazing incidence Incidence angle usually very low….~1-2° Reflection not from planes parallel to specimen surface reflecting plane

27 Thin films Relaxation Grazing incidence If incidence angle ~0.1-5° & intensity measured in symmetric geometry (incident angle = reflected angle), get reflectivity curve Relaxation Grazing incidence If incidence angle ~0.1-5° & intensity measured in symmetric geometry (incident angle = reflected angle), get reflectivity curve

28 Thin films Relaxation Need to measure misfit parallel to interface Use grazing incidence e.g., (224) or (113) Relaxation Need to measure misfit parallel to interface Use grazing incidence e.g., (224) or (113)

29 Thin films Relaxation Use grazing incidence e.g., (224) or (113) Need to separate tilt from true splitting Tilt effect reversed on rotation of = 180° Mismatch splitting unchanged on rotation Relaxation Use grazing incidence e.g., (224) or (113) Need to separate tilt from true splitting Tilt effect reversed on rotation of = 180° Mismatch splitting unchanged on rotation

30 Thin films Relaxation Use grazing incidence e.g, (224) or (113) For grazing incidence: i = + – splitting betwn substrate & layer Relaxation Use grazing incidence e.g, (224) or (113) For grazing incidence: i = + – splitting betwn substrate & layer

31 Thin films Relaxation Use grazing incidence e.g, (224) or (113) For grazing incidence: i = + e = – Can thus get both and Relaxation Use grazing incidence e.g, (224) or (113) For grazing incidence: i = + e = – Can thus get both and

32 Thin films Relaxation Also, And Relaxation Also, And

33 Thin films Relaxation Also, And Finally Relaxation Also, And Finally

34 Thin films Homogeneity Measure any significant parameter over a grid on specimen Ex: compositional variation get composition using Vegards law measure lattice parameter(s) – calculate relaxed mismatch Homogeneity Measure any significant parameter over a grid on specimen Ex: compositional variation get composition using Vegards law measure lattice parameter(s) – calculate relaxed mismatch

35 Thin films Homogeneity Measure any significant parameter over a grid on specimen Ex: variation of In content in InAlAs layer on GaAs Homogeneity Measure any significant parameter over a grid on specimen Ex: variation of In content in InAlAs layer on GaAs

36 Thin films Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness calculated curves

37 Thin films Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness Note thickness fringes Can use to estimate thickness Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness Note thickness fringes Can use to estimate thickness calculated curves

38 Thin films Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness Thickness For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness calculated curves


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