SCPY663 Thin Film Physics and Technology    Sample Problem Set of Part 1    General: 

SCPY663 Thin Film Physics and Technology Sample Problem Set of Part 1 General: 1. Draw a schematic sketch of: (a) an electronic device, (b) an optoelectronic device and (c) a magnetic head. Point out the materials used and the thickness and geometry of the films employed. Adsorption and Nucleation: 2. Assuming that the pre‐exponential factor for surface diffusion is given by kBT/h, (a) how low must the diffusion activation energy be to give a diffusion length, Λ, of roughly 100 nm between successive collisions with impinging vapor, for deposition of Si at 1 μm/hour and Ts = 400 °C. 3. For condensation onto non‐wetting substrates at 300 K using a 10‐4 Pa overpressure, what are the classical critical‐nucleus radii for Au, with γf =1.4 J⋅m‐2, neglecting substrate contact area and γf anisotropy? Evaporation: 4. Assume that aluminum is being evaporated at 1150K in a 25 cm2 cell. Show that the atomic flux at a distance of 0.5 m if the wafer is directly above the source is 4.8×1014 cm‐
2
sec‐1. Also show that the growth rate is approximately 48 Å/min (number density of aluminum is 6.0×1022 cm‐3). Electrical and optical properties: 5. A film of copper is 0.1 cm long, with a thickness of 100 nm and width of 2.0 μm. Calculate the resistance of the film. If a current of 10 mA flows in the film, what is the voltage and energy dissipated? Assume the resistivity of copper to be 1.7×10‐6 Ω‐cm. Given the density of copper to be 8.93 gm/cm3, how many copper atoms are in the film? Assuming each copper atom contributes one electron to conduction; calculate the mobility of electrons in the film. 6. Hall‐measurement was used to measure an electrical property of ITO film of 100 nm thick with the van de Pauw configuration. From the results, shown below, deduce its sheet resistivity, carrier mobility, carrier concentration. For explanation of configuration, you may have to access http://www.eeel.nist.gov/812/meas.htm#geom. Current = 1.000 mA Vab Vbc Magnetic field strength = 0.550 T
Vac Vmac V‐mac Film thickness= 0.100 µm Vcd Vda Vbd Temperature = 300 K
Vmbd V‐mbd +I: ‐19.267 ‐17.041 ‐2.254 ‐2.380 ‐2.112
‐19.272
‐17.046
‐2.247
‐2.113 ‐2.380
2.209
2.347 19.309
17.066
2.217
2.082 ‐I: 19.323 17.078 2.082
2.348
7. Show that light at 546 nm will reflect back to air (n=1.0) from thin ZnS (n=2.30) and TiO2 (n=2.6) films are 31% and 40%, respectively. Given that substrate is glasses (n=1.50) are coated with ZnS and TiO2 of 59.3 and 52.5 nm thick, respectively. Magnetic Properties: 8. The saturation flux density of iron is 2.18 Tesla. Show that approximately 2.19 electrons per atom are involved in contributing to ferromagnetism? (Hint: Bs = μ0Ms = μ0NnμB) Thin Film Analysis: 9. Thin TiO2 film is coated on a silicon substrate. This sample is analyzed with an RBS technique. The arrangement is shown in the figure show below. Intensity of back‐ scattered alpha particles is recorded as function of channel number (equivalent to energy) and is shown in the same figure. Estimate energies of back‐scattered alpha particles which scatter from the front side and the back side of TiO2, i.e., the right and the left flanks of titanium peaks. Assume that i) TiO2 is about 100 nm thick and ii) constant energy loss per unit length of TiO2. Figure 1 Top row: Arrangement of RBS measurement. Bottom row: Results for, Left: Silicon and Right: Glass, substrate