Uniform size of Si nanowire (NW) is highly desirable to enhance performance of Si NW based lithium ion batteries. To achieve narrow size distribution of Si NWs, formation of bulk-like...

achieved by interfacing two insulting oxides have attracted great attention in the past decade. [3][4][5][6][7][8][9][10] Different conduction mechanisms including polar catastrophe (interface), [5,10,11] strain, [12][13][14] intermixing (doping), [3,8,[15][16][17] and oxygen vacancy (defect) [18][19][20][21] have been proposed to explain such phenomenon. For example, carriers at the substrate-film interface (interface), bulk part of the film (film) and the surface layer of the substrate near the substratefilm interface (substrate surface layer) can all contribute to the effective conductivity of the samples. Polar catastrophe is a wellestablished model to explain the high conductivity at the interface between LaAlO 3 and SrTiO 3 (LAO/STO). [5,11,20] High mobility has also been reported when LaTiO 3 (LTO) and La 1-x Sr x TiO 3 (LSTO) are grown on SrTiO 3 (STO) [8,14,16,22] and KTaO 3 (KTO). [6] LTO is a polar perovskite like LAO, and as such, polar catastrophe mechanisms of this system are assumed to follow similarly to that of LAO/STO heterostructures. [5,11,20] However, unlike LAO, which is a band insulator, LTO is a Mott insulator that shows an insulator-metal transition when doped with Sr 2+ in polycrystalline bulk and epitaxial thin films. This allows the 3d 1 configuration to approach 3d 0 and may also result in the observed metallic behavior as reported in LSTO films on substrates such as (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (LSAT). [17,23] In addition, defects such as oxygen vacancy (OV) in the STO substrate are another factor which could affect the electric conductivity in STO-based heterostructures. The formation of OV in STO substrate is directly controlled by growth temperature and oxygen pressure as reported in different oxide/STO heterostructures. [5,15,18,20,21,[23][24][25][26][27][28] Enhanced conductivity is observed for these heterostructures grown (and STO single crystals annealed) in temperatures greater than 750 °C, at oxygen pressures lower than 10 -5 Torr or a combination of both. [29] For example, OVs can be introduced by reducing the STO substrate with pre-substrate annealing (PSA) at 750 °C and 10 -6 Torr. [28] Spinelli, et al. reported highly conductive STO crystals annealed at 10 -9 Torr and 700 °C. [29] Schneider et al. found substantial oxygen transfer from STO substrates to oxide films while studying the diffusion of isotope 18 O at the conditions of 750 °C and 1 × 10 -8 Torr. [19] Edmondson et al. observed STO substrate reduction at 10 -10 ~ 10 -7 Torr and 700 °C. [20] Therefore, the formation of OV near the STO surface or the diffusion of oxygen out A variety of mechanisms are reported to play critical roles in contributing to the high carrier/electron mobility in oxide/SrTiO 3 (STO) heterostructures. By using La 0.95 Sr 0.05 TiO 3 (LSTO) epitaxially grown on different single crystal substrates (such as STO, GdScO 3 , LaAlO 3 , (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 , and CeO 2 buffered STO) as the model systems, the formation of a conducting substrate surface layer (CSSL) on STO substr...

In article number 2101867, Zachary Corey, Quanxi Jia, Aiping Chen, and co-workers demonstrate that the growth of an oxide layer in a suitable condition can lead to oxygen transfer from the substrate to the film during growth. Such oxygen transfer forms a conductive substrate surface layer that contributes to the observed high carrier mobility.