1. Characterization of Thin Films
Modern techniques employed in the characterization of electronic
thin films and devices
Thickness
- Structure and Morphology surface
bulk irrespective of
ultimate applications
- chemical composition surface
bulk

3. 1.  Film Thickness
1.1  Optical methods
Interference of two or more beams of light whose optical path
difference is related to film thickness
Optical
Mechanical

4. Fizeau fringes of equal thickness (FET)

5. Quartz crystal oscillation
Deposition rate
Water-cooled shroud
1 Hz corresponds to 1.24x10-8 g of Al (0.46Å) for f=6MHz and A=1cm2

6. 2.  Structural characterization
TEM, SEM, XRD, STM, AFM, LEED, RHEED
3.  chemical characterization

7. Electron Spectroscopy – (EDX), AES, XPS

10. X-ray emission
Auger electron energy

11. AES & XPS spectrometer

12. Quantification by AES
XPS (Angle resolved)
Determination of chemical state by chemical shifts of XPS
- no damage on sample surface
- angle resolved XPS h e-  I0 x

13. XPS
Surface of AlGaAs etched in a
CF2Cl2 + O2 plasma

14. Rutherford Backscattering Spectrometer (RBS)
From energy & momentum conservation :
E0, M0: incident ion
E1: after elastic scattering
M: surface atom
: scattering angle
 = 170o
Kinematic factor
 depends just on the atomic weight of target atom
Kpt=0.922
Ksi=0.565

17. Peak height (H) is directly proportional to atomic concentration
Peak width (E) is directly proportional to film thickness
The concentration ratio
From figures

18. Measurement of Film Resistivity
J = nq J : electric current density
g : charge
 : velocity
 =   : mobility  : electric field
 J = nq
by Ohm’s law (J = )
: conductivity
 : resistivity
Film resistance
R = /wd

19. If  = w
“sheet resistance” with units of “ohms per square”
Ohms/
Lithographic patterning method
To avoid contact resistance
problem
4 points probe method for sheet
resistance
van der Pauw method
For resistivity

20. sheet resistance by 4-point probe method:
Resistivity : van der Pauw method for arbitrary points
Hall measurement : resistivity, carrier concentration, mobility

21. The electric field in the y-direction produces the Hall voltage VH

22. The Hall coefficient RH is defined as
Similarly, for n-type samples
The Hall mobility is defined as
Resistivity

23. Photoluminescence (PL)
- One of the most sensitive nondestructive methods
Characterization of the centers responsible for shallow donors
and acceptor species which control the electrical properties
and luminescence
Low temp. PL reduces the spectral broadening due to vibronic
processes

24. DA: donor acceptor pairs
CA: conduction band to acceptor
X: free excitons
D0X: excitons bound to
neutral donors
A0X: excitons bound to
neutral acceptors

25. Study of Interface roughness by PL
Exciton is used as probe
dBohr > Ls
dBohr < Ls