This document summarizes results from experiments depositing NiO films with varying oxygen concentrations in the gas mixture. Free path length calculations show path lengths decreasing slightly as oxygen concentration increases. X-ray diffraction analysis found the NiO7 film was under tensile stress while other films were compressive. Film thickness and crystal plane contribution varied depending on the deposition conditions and oxygen concentration, with the (200) plane increasing with more oxygen.

1. NiO results
Javier García Molleja
In collaboration with:
Julien Keraudy
Pierre-Yves Jouan

2. Free mean path
 Different gas mixtures used:
 Ni: 100% Ar – 0% O2
 NiO7: 87,72% Ar – 12,28% O2
 NiO9: 84,75% Ar – 15,25% O2
 NiO13: 79,37% Ar – 20,63% O2
 NiO19: 72,46% Ar – 27,54% O2
 Depositions at 3 cm of target substrate distance, at 5
mTorr of working pressure, DC power supply and 100 W
of power and 0,1 µTorr of base pressure.
 Target cleaning of 5 min with Ar plasma. Target
poisoning during 5-10 min.
 Substrates used: Si (100) and glass.

3. Free mean path
 Sigmund-Thompson distribution when Ar+
collides with Ni
target.
 [Kudriavtsev, 2005] proposes a binding energy of 3,74
eV.
 SRIM uses the approximation of heat of sublimation: 4,5
eV.
 If Ar+
has energy between 400-450 eV:
 Sputtering yield is 1,62-1,74 at/ion,
 Mean energy of sputtered Ni is 19,81-20,63 eV/at (SRIM
calculation) or 23,73-24,61 eV/at (theoretical values; using heat
of sublimation gives 26,89-27,95 eV/at),
 Ar backscattered is 5,64-5,78% of total impinging particles

4. Free mean path
 Particle travelling in a gas composed by many species
has a free mean path given by [Chen, 2005].
 Ni0
in 97% Ar – 3% Ar+
gas at 5 mTorr and 150 °C has a
λ=3,57 cm.
 Ni0
in Ar-O2 gas depends on molecular oxygen
percentage. It is assumed that ionization coefficient is
very low and in each discharge we have 80% O – 20%
O2 of reactive gas.
 NiO7: λ=3,509 cm.
 NiO9: λ=3,474 cm.
 NiO13: λ=3,411 cm.
 NiO19: λ=3,333 cm.
 There are no collisions during the trip.

5. Conduction mechanism
 Our NiO films, under such a high oxygen concentration
in the atmosphere has an oxygen excess.
 This process creates vacancies and electrical holes, so
NiO is a type-p conductor.
 Electrical holes are delocalized (band structure is over
the whole lattice), so Ni3+
localization is not definite a
priori.
 Two mechanisms are calculated, i.e., substitutional
process and interstitial process:

O2 2OO + 2V’’Ni + 4h
.

O2 O’’i + V’’Ni + OO + 4h
.
NiO
NiO

6. X-ray diffraction
 Parameters:
 CuKα @ 40 kV and 40 mA
 In and out slits: 1 mm
 Filter: Ni
 Scintillator slit: 0,2 mm
 Diffraction angle: 20-90°
 Steps: 0,03°
 Time: 1 s
 Technique: Bragg-Brentano

7. XRD: thickness
Ni

8. XRD: thickness
NiO7 NiO9

9. XRD: thickness
NiO13 NiO19

10. XRD: thickness (comparison)

11. XRD: bias
Ni

12. XRD: bias
NiO7 NiO9

13. XRD: bias
NiO13 NiO19

14. XRD: bias (comparison)

15. Thickness: plane contribution

16. Thickness: plane contribution

17. Thickness: plane contribution
 Area calculated by fitting with a Voigt function (ideal in X-
ray analyses).
 Different regimes of discharge:
 Metallic regime: Ni, NiO7
 Transition regime: NiO9
 Poisoned regime: NiO13, NiO19
 (111) and (200) planes are prominent in Ni and poisoned
conditions.
 In NiO7 other planes prevail.
 In NiO9 (222) planes appears.
 Oxygen augmentation provokes (200) increase.

18. Thickness: strain and grain size
NiO7
NiO13NiO7 is tensile. Other
samples are compressive.
High thickness produces
stress relief.

19. Bias: Plane contribution

20. Bias: plane contribution

21. Bias: plane contribution
 Area calculated by fitting with a Voigt function (ideal in X-
ray analyses).
 Different regimes of discharge:
 Metallic regime: Ni, NiO7
 Transition regime: NiO9
 Poisoned regime: NiO13, NiO19
 (111) and (200) planes are prominent in Ni and poisoned
conditions.
 In NiO7 other planes prevail.
 Oxygen augmentation provokes (200) increase.
 Bibliography says:
 (200) reduces surface energy
 (111) has a lot of adsorption sites, lower energy

22. Bias: stress and grain size
 [Mallikarjuna Reddy, 2011] has an
expresion to obtain residual stresses by
the peak shifting.
 Lorentz contribution has information about
the grain size using Scherrer’s formula.
 Lattice parameters have been calculated
by the Nelson-Riley method only for Kα1
contribution (a versus cotθcosθ).

23. Bias: stress and grain size
NiO7
NiO13
NiO7 is tensile. NiO13
changes with bias (from
compressive to tensile).