The influence of microstructure on stress state of sputter deposited chromium nitride films

Fabis, P. M.; Cooke, R.A.; McDonough, Steven

doi:10.1116/1.576455

Cited by 26 publications

(6 citation statements)

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“…This corresponds to a measured MgO lattice constant of 0.4211 nm, close to the literature value of 0.4212 nm 32 or 0.4213 nm, 33 and an out-of-plane CrN lattice constant of 0.4179 nm. This is in the range of reported bulk values, 0.4133-0.4185 nm, 10,15,[34][35][36] but likely indicates a slight compressive strain due to differential thermal contraction during cooling from the 850 °C growth temperature, similar to what has been previously reported for epitaxial CrN grown on MgO(001). 15 We note here that no secondary impurity phase is detected by XRD for all layers in this study.…”

Section: Optical Reflectance Was Measured With a Nicolet Magna Ir-560supporting

confidence: 87%

Variable-range hopping conduction in epitaxial CrN(001)

et al. 2011

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Epitaxial CrN(001) layers, grown by dc magnetron sputtering on MgO(001) substrates at growth temperatures T s = 550-850 °C, exhibit electronic transport that is dominated by variablerange-hopping (VRH) at temperatures <120 K. A transition from Efros-Shklovskii (ES) to Mott VRH at 30±10 K is well described by a universal scaling relation. The localization length decreases from 1.3 nm at T s = 550 °C to 0.9 nm for T s = 600-750 °C but increases again to 1.9 nm for T s = 800-850 °C, which is attributed to changes in the density of localized states associated with N-vacancies that form due to kinetic barriers for incorporation and enhanced desorption at low and high T s , respectively. The low-temperature transport data provides lower limits for the CrN effective electron mass of 4.9m e , the donor ionization energy of 24 meV, and the critical vacancy concentration for the metal-insulator transition of 8.4×10 19 cm-3. The room temperature conductivity is dominated by Hubbard band states near the mobility edge and decreases monotonically from 137 Ω-1 cm-1 for T s = 550 °C to 14 Ω-1 cm-1 for T s = 850 °C, due to a decreasing structural disorder, consistent with the measured x-ray coherence length that increases from 7 to 36 nm for T s = 550 to 850 °C, respectively, and a carrier density that decreases from 4×10 20 to 0.9×10 20 cm-3 , as estimated from optical reflection and Hall effect measurements. The absence of an expected discontinuity in the conductivity at ~280 K suggests that epitaxial constraints suppress the phase transition to a low-temperature orthorhombic antiferromagnetic phase, such that CrN remains a cubic paramagnetic insulator over the entire measured temperature range of 10-295 K. These results contradict previous experimental studies that report metallic low-temperature conduction for CrN, but support recent computational results suggesting a band gap due to strong electron correlation and a stress induced phase transition.

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Section: Optical Reflectance Was Measured With a Nicolet Magna Ir-560supporting

confidence: 87%

Variable-range hopping conduction in epitaxial CrN(001)

et al. 2011

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“…A narrow region of a typical XRD spectrum is shown in Fig. 2͑a͒ 43.54°, yielding a lattice constant a Ќ along the film growth direction of 0.4165 nm. The full width at half maximum intensity ⌫ 2 of the CrN 002 K ␣1 peak is 0.10°, only slightly larger than the value ⌫ 2 ϭ0.07°obtained for the MgO 002 K ␣1 substrate peak.…”

Section: Microstructure and Surface Morphologymentioning

confidence: 99%

“…41 We obtain a o ϭ0.4162Ϯ0.0008 nm, which is within the range of previously reported values, 0.4133-0.4185 nm, obtained from polycrystalline layers and bulk powder samples. 1,19,[42][43][44] Atomic force microscopy investigations reveal dramatic changes in CrN͑001͒ surface morphology as a function of J N 2 ϩ /J Cr . Figure 3 shows typical 3ϫ3 m 2 AFM images from 500-nm-thick CrN͑001͒ layers grown at T s ϭ600°C with incident ion-to-metal ratios of J N 2 ϩ /J Cr ϭ1.7 ͓Fig.…”

Section: Microstructure and Surface Morphologymentioning

confidence: 99%

Growth of single-crystal CrN on MgO(001): Effects of low-energy ion-irradiation on surface morphological evolution and physical properties

Gall

Shin

Spila

et al. 2002

Journal of Applied Physics

124

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CrN layers, 0.5 m thick, were grown on MgO͑001͒ at T s ϭ570-775°C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N 2 discharges at 20 mTorr. Layers grown at T s р700°C are stoichiometric single crystals exhibiting cube-on-cube epitaxy: (001) CrN ͉͉(001) MgO with ͓100͔ CrN ͉͉͓100͔ MgO. At higher temperatures, N 2 desorption during deposition results in understoichiometric polycrystalline films with N fractions decreasing to 0.35, 0.28, and 0.07 with T s ϭ730, 760, and 775°C, respectively. The surface morphologies of epitaxial CrN͑001͒ layers were found to depend strongly on the incident ion-to-metal flux ratio J N 2 ϩ /J Cr which was varied between 1.7 and 14 with the ion energy maintained constant at 12 eV. The surfaces of layers grown with J N 2 ϩ /J Cr ϭ1.7 consist of self-organized square-shaped mounds, due to kinetic roughening, with edges aligned along orthogonal ͗100͘ directions. The mounds have an average peak-to-valley height ͗h͘ϭ5.1 nm and an in-plane correlation length of ͗d͘ϭ0.21 m. The combination of atomic shadowing by the mounds with low adatom mobility results in the formation of nanopipes extending along the growth direction. Increasing J N 2 ϩ /J Cr to 14 leads, due to increased adatom mobilities, to much smoother surfaces with ͗h͘ϭ2.5 nm and ͗d͘ϭ0.52 m. Correspondingly, the nanopipe density decreases from 870 to 270 m Ϫ2 to Ͻ20 m Ϫ2 as J N 2 ϩ /J Cr is increased from 1.7 to 6 to 10. The hardness of dense CrN͑001͒ is 28.5Ϯ1 GPa, but decreases to 22.5Ϯ1 GPa for layers containing significant nanopipe densities. The CrN͑001͒ elastic modulus, 405Ϯ15 GPa, room-temperature resistivity, 7.7ϫ10 Ϫ2 ⍀ cm, and relaxed lattice constant, 0.4162Ϯ0.0008 nm, are independent of J N 2 ϩ /J Cr .

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“…[1][2][3][4] Other characteristics of CrN include a high hardness, a high toughness, and a low mechanical stress. [9][10][11][12] There are two stable phases of chromium nitride at room temperature: Cr 2 N and CrN. [9][10][11][12] There are two stable phases of chromium nitride at room temperature: Cr 2 N and CrN.…”

Section: Introductionmentioning

confidence: 99%