question 1

(*)Which technique(s) is(are) commonly used to determine the quality of epitaxial growth of thin films?

A XRR (X-ray reflection)
B XRD (X-ray diffraction)
C RHEED (Reflection high energy electron diffraction)
D THEED (Transmission high energy electron diffraction)
E RLEED (Reflection low energy electron diffraction)

question 2

(*)What is correct in general?

A the thinner the thin film, the higher the resistance
B the thicker the thin film, the higher the resistance
C the thinner the thin film, the higher the resistivity
D the thicker the thin film, the higher the resistivity

question 3

(*)Which of the following is the most undesirable dislocation mechanisms of relaxation in films:

A film cracking
B diffusional creep
C dislocation glide
D dislocation climb

question 4

(*2)What is true about electrical resistivity?

A The resistivity of a semiconductor increases as the temperature decreases from room temperature
B The resistivity of metals increases as the temperature decreases from room temperature
C The resistivity of metals does not depend on temperature
D Matthiessen's rule says that the resistivity of a single-crystalline metal is the sum of the resistivity due to thermal vibrations of the lattice (phonons) and the resistivity due to defects in the crystal
E Matthiessen's rule says that the electrical conductivity of a single-crystalline metal is the sum of the conductivity due to thermal vibrations of the lattice (phonons) and the conductivity due to electrical shorts in the crystal

question 5

(*2)What is the resistance of the structures between points 1 and 2 knowing that the resistance per square is 1 ohm?
Take the effective resistance of the corner squares in C) to be 0.55 ohms.

A A/B/C = 5.0/2.5/8.0 ohms
B A/B/C = 5.0/10.0/8.0 ohms
C A/B/C = 5.0/5.0/14.2 ohms
D A/B/C = 5.1/5.1/7.1 ohms
E A/B/C = 5.0/5.0/7.1 ohms
F Not enough data

question 6

(*)What makes thin films different from the bulk?

A Thin films are always electrically conducting
B Properties of thin-films and bulk materials are always the same
C Size effects
D High dislocation density
E High electric fields are not easily attainable
F Low chemical reactivity

question 7

(*)Which of the following mechanisms of relaxation in thin films is most unwanted?

A Dislocation glide.
B Dislocation climb.
C Diffusional creep.
D Film cracking.

question 8

What is/are correct for metals in general?

A Are transparent for visible light
B Have relatively high plasticity
C Have resistivity which increases with temperature
D Have a sea of free electrons that makes metals good conductors of heat
E Are amorphous

question 9

Sheet resistance is related to the bulk resistivity (rho). The sheet resistance is equivalent to

A rho*width
B rho/width
C rho*thickness
D rho/thickness

question 10

(*2) The four-probe method for resistance/resistivity measurements is preferred over the two-probe one. Why?

A To assure a constant potential drop across the specimen
B To minimize the contact resistances
C To exclude the contact resistances from the measurement
D To stabilize the current through the specimen
E To avoid damage of the specimen

question 11

(*)Which of the following statement(s) is (are) not true?

A A thin film deposited on a substrate with equal thermal coefficient of expansion does not develop stress
B Mismatch in the thermal coefficients of expansion can result in a stressed film
C The thinner the film the stronger the stress
D Lattice mismatch between the film and substrate induces stress in thin films
E Internal stress in thin films affects its adhesion to the substrate

question 12

(*)Why does the breakdown voltage increase when lowering P*D below the minimum of the Paschen's curve? Here, P is the pressure and D is the distance between the electrodes inside the chamber.

A the two electrodes are too close that requires higher voltage for charged particles to gain high enough (ionization) energy on their way from one electrode to another
B the pressure is too low to give rise to discharge
C low pressure means fewer neutral and charged particles to be able to collide with each other
D the pressure is too high to give rise to discharge

question 13

(*3) The residual resistivity of a metal thin film at low temperature

A is proportional to the density of defects
B is inversely proportional to the density of defects
C depends on the metal
D depends on the thickness for high-purity and low-defect thin films
E depends on the specimen length and width (larger than the thin film thickness)
F depends neither on the specimen length nor its width (larger than the thin film thickness)

question 14

(*3) Take a 100-nm thin film with the sheet resistance of 10 ohms. What is the resistance of the 1x1 mm^2 and 1x1 cm^2 large squares cut out of this film? Assume that the current is applied uniformly to the opposite sides of the square and ignore the contact resistances.

A 1 ohm in both cases
B 10 ohms in both cases
C 100 ohms in both cases
D 10 and 100 ohms, respectively
E 10 and 1 ohms, respectively
F 1 and 100 ohms, respectively
G 100 and 1 ohms, respectively
H there is a factor of 10 or 100 difference between the resistances; the smaller square has larger resistance
I there is a factor of 10 or 100 difference between the resistances; the smaller square will has smaller resistance
J it is not possible to calculate the resistances in this case without knowing the resistivity of the material
K the values given are unrealistic

question 15

For which conditions will a thin film have larger grains?

A High deposition rate and high substrate temperature
B High deposition rate and low substrate temperature
C Low deposition rate and high substrate temperature
D Low deposition rate and low substrate temperature

question 16

What does "critical thickness" mean in epitaxial films?

A Minimum thickness of defect-free layer
B Thickness of substrate needed for epitaxial growth of film on it
C Maximum thickness of defect-free layer
D The film lattice would compensate for dislocation defects above this thickness.