Nanoscale composition analysis of atomically flat SrTiO3(001) by friction force microscopy

Abstract

Friction force microscopy ͑FFM͒ was used to distinguish the different surface terminations on the nanoscale on atomically flat SrTiO 3 ͑001͒ surfaces, obtained by a combination of ultrasonic agitation and subsequent annealing in air at 1000°C. The surface exhibits atomically flat terraces and sharp steps whose height is 0.2 nm, corresponding to half the height of a unit cell of SrTiO 3 , or a single atomic layer, where strong friction contrast appears. A compositional analysis of the topmost surface by coaxial-impact-collision ion-scattering spectroscopy ͑CAICISS͒ indicated that the friction contrast corresponded to different surface terminations, namely, the SrO and TiO 2 layer as a topmost surface, where the TiO 2 domain was dominant. This is further supported by the correlation between the compositional Sr/Ti ratio and the area ratio which was observed by CAICISS and FFM, respectively.

Effect of water adsorption on microscopic friction force on SrTiO3(001)

“…The wide terrace showing weaker friction is made up of a TiO 2 layer and the small terrace showing stronger friction is made up of SrO, which is confirmed in our previous report by comparing the area ratio observed by AFM/FFM with the compositional ratio observed by coaxial impact collision ion scattering spectroscopy. 6,8 In Figs. 1͑c͒ and 1͑d͒, a topographic image and a phase image taken by tapping-mode AFM for the same sample are shown.…”

“…The former consists of a TiO 2 layer and the latter, a SrO layer which is determined by combinatory analysis of FFM, and coaxial impact collision ion scattering spectroscopy. 6,8 These layers show a strong friction contrast in the FFM image observed under atmospheric conditions, where the friction force on the SrO layer, or the narrow terrace, is two times stronger than that on TiO 2 , or the wide terrace. The samples possessing these features were investigated in this study.…”

Surface phase, morphology, and charge distribution transitions on vacuum and ambient annealedSrTiO3(100)

“…4a), we only find terraces separated by unit cell step height (3.905 Å; marked by the blue dotted lines), which implies that the surface is uniformly covered by the same termination. [16,20,25] Interestingly, after annealing ( Fig. 4b-d observed.…”

“…Since both layers are thermodynamically stable and non-polar, a (100) surface in principle can expose either of the two terminations, making the properties of the surface a local characteristic. [14][15][16][17][18][19][20][21][22][23] Given that SrO-and TiO 2 -terminated terraces differ substantially in their chemical and electrical properties, [14,[24][25][26][27][28][29] the characteristics of films grown on nominally mixedterminated substrates will vary locally as well. Similar to many other perovskite metal oxides, SrTiO 3 commonly reconstructs; the plethora of reconstructions identified include (2×1), (2×2), (4×4), c(4×2), c(4×4), c(6×2), (√5×√5)-R26.6°, and (√13×√13)-R33.7° structures.…”

Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

“…27 This approach has been previously employed to determine the local termination of complex-oxide surfaces and in particular to probe the partial SrO coverage on the surface of STO single-crystals. 30,31 Figures 3(a) and 3(b) show the surface topography and the FFM images, respectively, of a single-crystalline (001) STO substrate. Unit-cell-high step-and-terrace structure, a characteristic feature of a miscut TiO 2 -terminated STO surface, can be clearly seen on the topographic image.…”