[PDF]    http://dx.doi.org/10.3952/lithjphys.50302

Open access article / Atviros prieigos straipsnis

Lith. J. Phys. 50, 317–323 (2010)

S. Mickevičiusa, S. Grebinskija, V. Bondarenkaa,b, H. Tvardauskasa, M. Senulisa, V. Lisauskasa, K. Šliužienėa, B. Vengalisa, B.A. Orlowskic, and E. Baškysa
aSemiconductor Physics Institute, Center for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius, Lithuania
bVilnius Pedagogical University, Studentų 39, LT-08106 Vilnius, Lithuania
cInstitute of Physics of the Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
E-mail: sigism@pfi.lt

Received 3 December 2009; revised 23 June 2010; accepted 16 September 2010

Thin LaNiO3−δ films with pseudocubic (100) preferred orientation were prepared by reactive DC magnetron sputtering and in situ annealed in O2 and vacuum. X-ray photoelectron spectroscopy (XPS) was used to determine the variation in composition of the films under high temperature annealing. The experimental O 1s and La 3d – Ni 2p3/2 spectra of LaNiO3−δ films was analysed in terms of O2−, O/(OH), and weakly adsorbed oxygen species. It was shown that the change in the type of conductivity from metallic to semiconducting one is accompanied by a marked increase in the intensity of the lateral (~531 eV) peak of oxygen. The quantitative analyses of La 3d – Ni 2p3/2 spectra show that the Ni/La concentration ratio significantly decreases after heating above the dehydration temperature. These variations in conductivity and surface composition were attributed to the loss of lattice oxygen with subsequent adsorption of O and (OH) anions and weakly adsorbed oxygen species from ambient air.
Keywords: rare earth alloys and compounds, oxide materials, XPS, surfaces and interfaces, LaNiO3 thin film
PACS: 68.60.Dv, 79.60.Dp

S. Mickevičiusa, S. Grebinskija, V. Bondarenkaa,b, H. Tvardauskasa, M. Senulisa, V. Lisauskasa, K. Šliužienėa, B. Vengalisa, B.A. Orlowskic, E. Baškysa
aFizinių ir technologijos mokslų centro Puslaidininkių fizikos institutas, Vilnius, Lietuva
bVilniaus pedagoginis universitetas, Vilnius, Lietuva
cLenkijos mokslų akademijos Fizikos institutas, Varšuva, Lenkija

Plonieji daugiausia pseudokubine (100) kryptimi orientuoti LaNiO3−δ sluoksniai gaminti reaktyvinio nuolatinės srovės magnetroninio dulkinimo būdu ir in situ atkaitinti O2 ir vakuume. Sluoksnių sudėties kitimas kaitinimo metu tirtas Rentgeno fotoelektroninės spektroskopijos (RFS) metodu. Ištirti eksperimentiniai LaNiO3−δ sluoksnių O 1s ir La 3d – Ni 2p3/2 spektrai, siekiant nustatyti O2−, O/(OH) ir silpnai surišto deguonies santykius. Metalinio laidumo virtimą puslaidininkiniu atkaitinant vakuume aukštoje temperatūroje lydi žymus O 1s spektro 531 eV smailės intensyvumo padidėjimas. Šis intensyvumo augimas sietinas su deguonies vakansijų koncentracijos augimu ir lygiagrečiai su deguonies jonų su nutrauktais cheminiais ryšiais skaičiaus padidėjimu. Kiekybinė La 3d – Ni 2p3/2 spektro analizė rodo žymų Ni/La koncentracijų santykio sumažėjimą atkaitinus virš dehidracijos temperatūros. Toks laidumo ir paviršiaus sudėties kitimas aiškintinas deguonies netekimu gardelėje su vėlesne O ir (OH) anijonų bei silpnai surišto deguonies adsorbcija iš aplinkos oro.

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