thin films

aSGuest101691

Download

Post to :

URL :

Related Presentations :

Add to Flag Embed

Views: 49

Category: Entertainment

Presentation Description

No description available.

Comments

Presentation Transcript

Slide 1:

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

Slide 2:

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

Slide 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

Slide 4:

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

Slide 5:

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

Slide 6:

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

Slide 7:

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

Slide 8:

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

Slide 9:

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

Slide 10:

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

Slide 11:

Thin films Mismatch constrained relaxed

Slide 12:

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

Slide 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  = 90° 

Slide 14:

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

Slide 15:

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

Slide 16:

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

Slide 17:

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

Slide 18:

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

Slide 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

Slide 20:

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

Slide 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

Slide 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

Slide 23:

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

Slide 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

Slide 25:

Slide 26:

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

Slide 27:

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

Slide 28:

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

Slide 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

Slide 30:

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

Slide 31:

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

Slide 32:

Thin films Relaxation Also, And

Slide 33:

Thin films Relaxation Also, And Finally

Slide 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

Slide 35:

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

Slide 36:

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

Slide 37:

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

Slide 38:

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