Nanoindentation of Chromium Oxide Possessing Superior Hardness among Atomic-Layer-Deposited Oxides

Abstract

Chromium (III) oxide is a technologically interesting material with attractive chemical, catalytic, magnetic and mechanical properties. It can be produced by different chemical and physical methods, for instance, by metal–organic chemical vapor deposition, thermal decomposition of chromium nitrate Cr(NO3)3 or ammonium dichromate (NH4)2Cr2O7, magnetron sputtering and atomic layer deposition. The latter method was used in the current work to deposit Cr2O3 thin films with thicknesses from 28 to 400 nm at deposition temperatures from 330 to 465 °C. The phase composition, crystallite size, hardness and modulus of elasticity were measured. The deposited Cr2O3 thin films had different structures from X-ray amorphous to crystalline α-Cr2O3 (eskolaite) structures. The averaged hardness of the films on SiO2 glass substrate varied from 12 to 22 GPa and the moduli were in the range of 76–180 GPa, as determined by nanoindentation. Lower values included some influence from a softer deposition substrate. The results indicate that Cr2O3 could be a promising material as a mechanically protective thin film applicable, for instance, in micro-electromechanical devices.

Mechanical and Optical Properties of Cr2O3 Thin Films Grown by Atomic Layer Deposition Method Using Cr(thd)3 and Ozone

“…It can be predicted that the growth of the film proceeds in different stages-starting with a preferential orientation type up to the thickness of approximately 20 nm, followed by the relatively intensive formation of crystallites with asymmetric shapes in the range of t = 20-50 nm, and finishing with the enlargement of the already grown crystallites and possibly also with the formation of new crystallites whose orientation is determined by the presence and orientation of the underlying crystallites. An increase in crystallite size by increasing the film thickness for Cr 2 O 3 films using CrO 2 Cl 2 and CH 3 OH was reported previously [48].…”

Multicolor Bipolar Modulation of Titanium–Chromium Oxide Electrochromic Coatings

“…Furthermore, from Figure S4, we can see a higher surface roughness and larger crystal size with increased Cr atomic concentrations. Previous literature reporting on the crystallinity of ALD-deposited TiO 2 and CrO x also suggests that a growth temperature of 375 °C would encourage the formation of polycrystallines rather than amorphous films. − This growth behavior combined with the materials characterizations indicates that the tendency of nucleation or cluster formation for Ti:Cr = 2:1 was due to the high growth temperature (375 °C) and the high Cr concentration.…”

Activated Sintering of Cr2O3-Based Composites by Hot Pressing

“…This might be the main explanation for the different microhardness values of dark and light phases, which were measured as HV d = 26 ± 0.15 GPa and HV l = 12 ± 0.5 GPa, respectively, under the load of 520 g. Moreover, the increased microhardness of chromium itself may be attributed to the additions of aluminum and iron since it is highly dependent on the technology and related additions and thus varies between HV = 2 and HV = 10 GPa [ 38 ]. Noteworthily, nanoindentation revealed the hardness of Cr 2 O 3 thin films on SiO 2 glass substrate ranging from 12 to 22 GPa [ 39 ].…”