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Author(s)
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Qi, B (Iceland U.) ; Gunnlaugsson, H P (Iceland U.) ; Mokhles Gerami, A (K.N. Toosi U.) ; Gislason, H P (Iceland U.) ; Ólafsson, S (Iceland U.) ; Magnus, F (Iceland U.) ; Mølholt, T E (CERN) ; Masenda, H (U. Witwatersrand, Johannesburg, Sch. Phys.) ; Tarazaga Martín-Lueugo, A (Linz U.) ; Bonanni, A (Linz U.) ; Krastev, P B (Sofiya, Inst. Nucl. Res.) ; Masondo, V (KwaZulu Natal U.) ; Unzueta, I (Basque U., Bilbao) ; Bharuth-Ram, K (KwaZulu Natal U. ; DUT, Durban) ; Johnston, K (CERN) ; Naidoo, D (U. Witwatersrand, Johannesburg, Sch. Phys.) ; Schell, J (CERN ; Duisburg-Essen U.) ; Schaaf, P (Ilmenau Tech. U.) |
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Abstract
| The properties and performance of TiN thin films are closely related to the concentration and mobility of lattice defects in the thin film structures of TiN. This makes a local atomic scale study of TiN thin films an ever-growing demand. Emission $^{57}$Fe Mössbauer spectroscopy (eMS) is a powerful tool in this regard, which we apply here to study an ultrathin TiN film epitaxially grown on MgO (1 0 0). With the help of theoretical calculations, our results show that most implanted Fe ions adopt a 2$^{+}$ valence state and locate at the Ti sublattice in the bulk-like single crystalline grains, with the rest Fe residing at the grain boundaries as interstitials. A small percentage of nitrogen point defects (vacancy V$_{N}$ and interstitial N$_{I}$) are observed in the bulk-like crystalline grains. A temperature-dependent, interstitial N$_{I}$ mediated site-exchange between N$_{I}$ and V$_{N}$ inside the crystal grain are deduced via a N$_{2}$ dimmer like diffusion of N$_{I}$ through the crystal grains in the temperature range of 540–620 K. This is interesting in the perspective of exploring the catalytic property of TiN nanostructures. The titanium vacancy(V$_{Ti}$) is only detected at the grain boundaries. Annealing up to 813 K, both the V$_{N}$ and N$_{I}$ are annihilated in the crystalline grains and the V$_{Ti}$ is fully recovered with healing of the grain boundaries. However, no evidence of ferromagnetism due to dilute implantation of $^{57}$Mn/$^{57}$Fe and or structural defects in the film is obtained. This suggests that the so far reported dilute magnetism and defect-induced ferromagnetism in TiN nanostructures requires a further systematic investigation. |