Q2. What was the purpose of the study?
Elastic recoil detection analysis (ERDA), by a 35 MeV Cl7+ ion beam incident at anangle of 15° with respect to the sample surface, was used to measure the chemical composition.
Q3. What is the effect of phase control on Al2O3 thin films?
The existence of severalmetastable phases complicates growth of α-Al2O3, especially when low temperature growth is required (to limit the thermal load of the substrate).
Q4. What is the effect of the sputtering on the phase?
Theformation of the α phase occurred only at a low total pressure (0.33 Pa), suggesting that it waspromoted by a high energetic bombardment of the growth surface.
Q5. What is the effect of the oxidization on the target voltage?
The oxidization is also accompanied by a drop in deposition rate by morethan an order of magnitude, due to the decrease in sputter yield and increase in secondary electron yield.7, 8 Interestingly, at 7 mPa O2 the deposition rate had already decreased by more than 50%, while the target voltage was almost unaffected.
Q6. What was the effect of water on the crystalline structure of the films?
All AlOx depositions were subsequently made onto electrically floating substrates at a temperature of 500 °C, while the totalAr+O2 and the partial O2 pressures could be varied (the O2 pressure was measured during sputtering by a differentially pumped mass spectrometer).
Q7. What is the effect of the alumina film on the substrate?
In high vacuum deposition systems significantly higher amounts (compared to UHVconditions) of residual gases are present during the film growth.
Q8. What is the effect of the low total pressure on the oxidization rate?
The low total pressure implies that a larger part of the energetic particles originating from the target willretain their initial energy.
Q9. What is the effect of the oxidized oxygen particles on the substrate?
The energetic oxygen particles originate from the oxidized parts of thetarget surface as negative ions and are accelerated to high energies over the target sheath voltage (in their case 300-500 V), as shown by Tominaga et al.15 for reactive sputtering of Zn.
Q10. What is the phase change in the films?
The films exhibit a phase change as the O2 partial pressure increases from 7 to 16 mPa (corresponding to deposition rates of about 40% and 20% of the rate in pure Ar).
Q11. How was the crystalline structure of the films studied?
in order to study the effect of water, which is known to be important in alumina growth,5 films were deposited both at ultra high vacuum (UHV) and in a background of ~10-4 Pa H2O.
Q12. What is the reason for the decrease in deposition rate?
A qualitative estimation, using the Berg model for reactive sputtering,10 showed that this was due to thecombination of small target area and high pumping speed (~400 l/s).
Q13. How was the crystalline phase of the films identified?
The crystalline phases ofthe deposited films were identified by grazing incidence x-ray diffraction (GIXRD) at an incident angle of 4°.
Q14. what is the alumina phase control method?
α-Al2O3 films were achieved at 760 °C by pulsed DC reactive magnetron sputtering,1 at 580 °C using plasma assisted chemical vapor deposition,2 and at 280 °C by non-reactive RF magnetron sputtering from an Al2O3 target using chromia (Cr2O3) nucleation layers.3, 4 In this article, the method of a chromia “template” is applied to reactive magnetron sputtering, with the aim tounderstand and control alumina growth at low temperatures.
Q15. How can the phase content of the films be controlled?
these studies show that low-temperature growth of α-Al2O3 is possible by reactive sputtering and that the phase content of the films can be controlled by controlling the kineticenergy of the depositing species.
Q16. How does the GIXRD results compare to the UHV case?
A rough estimation using atomic radii yields mean free paths in Ar of 16and 8 cm, for O, and 5 and 2.5 cm, for Al, at 0.33 and 0.67 Pa, respectively.
Q17. What is the reason for the phase change?
The phase changes might instead be explained by an increased bombardment of the growthsurface by energetic particles, increasing the mobility at the surface.
Q18. What is the oxidization rate of the AlOx films?
The three O2 partial pressures (16, 24, and 32 mPa) correspond to deposition rates of about 35%, 20%, and 15%, respectively, of the rate in pure Ar (absolute rates are found in Table I).
Q19. How did the authors study alumina thin films?
In summary, the authors have studied alumina thin films grown by reactive magnetron sputtering atlow temperatures (500 °C), both at UHV and in a background of ~10-4 Pa H2O.
Q20. How many % of the alumina films are sputtered?
At a target-to-substrate distance of 11 cm, this corresponds to probabilities for reaching the substrate without anycollisions of 50 % and 25 %, respectively, for O and 6 % and 0.4 % for Al.
Q21. How did the GIXRD results from these films compare to the UHV results?
Inorder to study its effect on low-temperature growth of α-Al2O3, films were deposited in a (high vacuum) background of ~10-4 Pa H2O at a total pressure of 0.33 Pa, substrate temperature of 500 °C, and O2 partial pressures of 16 and 103 mPa.