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 defectsCommon epilayer defects

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

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

Thin filmsThin 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

Thin filmsThin films

Common epilayer defects

Investigate using rocking curves

Broadens layer peakinvariant w/ beam sizepeak position invariant

w/ sample position

Common epilayer defects

Investigate using rocking curves

Broadens layer peakinvariant w/ beam sizepeak position invariant

w/ sample position

Thin filmsThin films

Common epilayer defects

Investigate using rocking curves

Broadens layer peakmay increase w/ beam

sizepeak position invariant

w/ sample position

Common epilayer defects

Investigate using rocking curves

Broadens layer peakmay increase w/ beam

sizepeak position invariant

w/ sample position

Thin filmsThin films

Common epilayer defects

Investigate using rocking curves

Broadens layer peakincreases w/ beam sizepeak position varies

w/ sample position

Common epilayer defects

Investigate using rocking curves

Broadens layer peakincreases w/ beam sizepeak position varies

w/ sample position

Thin filmsThin 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

Thin filmsThin 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

Thin filmsThin films

Investigate using rocking curves

Film thickness

Integrated intensity changesincreases w/ thickness

Interference fringes

Investigate using rocking curves

Film thickness

Integrated intensity changesincreases w/ thickness

Interference fringes

Thin filmsThin films

MismatchMismatch

constrained relaxed

Thin filmsThin 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

Thin filmsThin films

Misorientation

First, determine orientation of substrate

rotate to bring plane normal into counter plane

do scans at this positionand at + 180°

orientation angle = 1/2difference in two angles

Misorientation

First, determine orientation of substrate

rotate to bring plane normal into counter plane

do scans at this positionand at + 180°

orientation angle = 1/2difference in two angles

= 90°

Thin filmsThin 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 +

Thin filmsThin 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 –

Thin filmsThin 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

Thin filmsThin 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

Thin filmsThin films

Dislocations

From:high mismatch strain, locally relaxedlocal plastic deformation due to straingrowth dislocations

Dislocations

From:high mismatch strain, locally relaxedlocal plastic deformation due to straingrowth dislocations

Thin filmsThin films

Dislocations

From:high mismatch strain, locally relaxedlocal plastic deformation due to straingrowth dislocations

Estimate dislocation density from broadening (radians)

& Burgers vector b (cm):

= 2/9b2

Dislocations

From:high mismatch strain, locally relaxedlocal plastic deformation due to straingrowth dislocations

Estimate dislocation density from broadening (radians)

& Burgers vector b (cm):

= 2/9b2

Thin filmsThin 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"

Thin filmsThin films

Relaxation

Need to measure misfit parallel to interface

Both mismatch &misorientation changeon relaxation

Interplanar spacings change with mismatch distortion & relaxation – changes splittings

Relaxation

Need to measure misfit parallel to interface

Both mismatch &misorientation changeon relaxation

Interplanar spacings change with mismatch distortion & relaxation – changes splittings

Thin filmsThin films

Relaxation

Need to measure misfit parallel to interface

Both mismatch &misorientation changeon relaxation

So, also need misfit perpendicular to interface

Then, % relaxation is

Relaxation

Need to measure misfit parallel to interface

Both mismatch &misorientation changeon relaxation

So, also need misfit perpendicular to interface

Then, % relaxation is

Thin filmsThin films

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Limits penetration ofspecimen

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Limits penetration ofspecimen

reflectingplane

Thin filmsThin films

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Limits penetration ofspecimen

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 ofspecimen

Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen

Thin filmsThin films

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Limits penetration ofspecimen

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 ofspecimen

Penetration depth – G(x) = fraction of total diffracted intensity from layer x cm thick compared to infinitely thick specimen

Thin filmsThin films

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Reflection not fromplanes parallel to specimen surface

Relaxation

Grazing incidence Incidence angle usually

very low….~1-2°

Reflection not fromplanes parallel to specimen surface

reflectingplane

Thin filmsThin 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

Thin filmsThin films

Relaxation

Need to measure misfit parallel to interface

Use grazing incidencee.g., (224) or (113)

Relaxation

Need to measure misfit parallel to interface

Use grazing incidencee.g., (224) or (113)

Thin filmsThin films

Relaxation

Use grazing incidencee.g., (224) or (113)

Need to separate tiltfrom true splitting

Tilt effect reversedon rotation of = 180°

Mismatch splittingunchanged on rotation

Relaxation

Use grazing incidencee.g., (224) or (113)

Need to separate tiltfrom true splitting

Tilt effect reversedon rotation of = 180°

Mismatch splittingunchanged on rotation

Thin filmsThin films

Relaxation

Use grazing incidencee.g, (224) or (113)

For grazing incidence:

i = +

– splitting betwn substrate & layer

Relaxation

Use grazing incidencee.g, (224) or (113)

For grazing incidence:

i = +

– splitting betwn substrate & layer

Thin filmsThin films

Relaxation

Use grazing incidencee.g, (224) or (113)

For grazing incidence:

i = +

e = –

Can thus get bothand

Relaxation

Use grazing incidencee.g, (224) or (113)

For grazing incidence:

i = +

e = –

Can thus get bothand

Thin filmsThin films

Relaxation

Also,

And

Relaxation

Also,

And

Thin filmsThin films

Relaxation

Also,

And

Finally

Relaxation

Also,

And

Finally

Thin filmsThin films

Homogeneity

Measure any significant parameter over a grid on specimen

Ex: compositional variation

get composition using Vegards lawmeasure lattice parameter(s) – calculate relaxed

mismatch

Homogeneity

Measure any significant parameter over a grid on specimen

Ex: compositional variation

get composition using Vegards lawmeasure lattice parameter(s) – calculate relaxed

mismatch

Thin filmsThin 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

Thin filmsThin 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 curvescalculated curves

Thin filmsThin films

Thickness

For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness

Note thickness fringes

Can use to estimatethickness

Thickness

For simple structure layer, layer peak integrated intensity increases monotonically w/ thickness

Note thickness fringes

Can use to estimatethickness

calculated curvescalculated curves

Thin filmsThin 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 curvescalculated curves