La₂O₃ thin films were prepared by a sol–gel method and annealed in air and vacuum at various temperatures. The X-ray photoelectron spectroscopy (XPS) was used to investigate the properties and composition of films. The La 3d and O 1s spectra of films were analysed. It was shown that oxygen ions in La₂O₃ are in two states – O^2– anions connected with lanthanum, and oxygen in the (OH)– group. The thermal transformation of lanthanum hydroxide to oxide process was triggered by thermal treatment at temperatures above 600 K. It was shown that after annealing thin films for longer time intervals in vacuum the intensity of O^2– component increases and the intensity of oxygen in (OH)– decreases. The drop of oxygen in the (OH)– group was attributed to dehydration process.

Keywords: La₂O₃ thin films, sol–gel method, XPS, oxide materials
PACS: 61.05.C-, 71.15.Nc, 81.20.Fw

ZOLIŲ-GELIŲ METODU PAGAMINTŲ PLONŲJŲ LANTANO OKSIDO SLUOKSNIŲ XPS TYRIMAS
E. Baškys^a, V. Bondarenka^a,b, S. Grebinskij^a, M. Senulis^a, R. Sereika^b
aFizinių ir technologijos mokslų centro Puslaidininkių fizikos institutas, Vilnius, Lietuva
^bLietuvos edukologijos universiteto Gamtos, matematikos ir technologijų fakultetas, Vilnius, Lietuva

Plonieji La₂O₃ sluoksniai pagaminti naudojant zolių-gelių technologijos metodus. Po sluoksnių sintezės jie buvo termiškai apdorojami oro atmosferoje ir vakuume (10^–7 Pa) temperatūrų intervale 673–823 K nuo 2 iki 92 val. Po kiekvieno apdorojimo ciklo buvo matuojami bandinių rentgeno fotoelektronų spektrai (XPS).
Nustatyta, kad nepriklausomai nuo apdorojimo režimo (temperatūros ir laiko) lantano jonai bandiniuose yra stabilios La³⁺ būsenos. Visais atvejais deguonies O 1s RFS smailė turi savyje dvi dedamąsias su ryšio energijomis ~528 ir ~531 eV, kurios atitinka O^2– jonus oksido gardelėje ir deguonį, surištą hidroksilinėje grupėje (OH)^–. Didėjant bandinių apdorojimo temperatūrai ir laikui didėja O^2– jonų koncentracija bei mažėja deguonies kiekis (OH)^– grupėje.
Visuose bandiniuose nepastebėta absorbuoto vandens. Po terminio bandinių apdorojimo vakuume aptikta mažėjanti (OH)^– grupių koncentracija leidžia manyti, kad, tinkamai parinkus technologinius sluoksnių terminio atkaitinimo vakuume režimus (panaudojant zolių-gelių sintezės metodus), galima gauti nehigroskopinius lantano oksido sluoksnius.

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