Identifying high-voltage cathode materials is critically important for increasing the energy density of Na ion batteries. Through a comprehensive density-functional survey, we demonstrate that oxygen redox in $R\overline{3}$ (ilmenite structure) $\mathrm{N}{\mathrm{a}}_{1}M{\mathrm{O}}_3$ generates high operating voltage upon extraction and insertion of a Na ion. In the $R\overline{3}$ structure, O ions are undercoordinated by two $M$ and two Na ions and two vacant sites, creating unhybridized O $2p$ states with a nonbonding character that are lifted closer to the Fermi level. Since O $2p$ and $M t_{2g}$ states do not significantly overlap at the top of the valence band, the redox reaction is mainly borne on O ions. We also show that, in general, higher covalent bonding between the transition metal and oxygen results in higher voltage in this class of materials in which O redox is dominant. Furthermore, a thorough examination of the phase stability of $R\overline{3} {\mathrm{Na}}_{1}M{\mathrm{O}}_3$ compounds reveals that $\mathrm{N}{\mathrm{a}}_1\mathrm{V}{\mathrm{O}}_3$ is an economical high-voltage (5.907 V) cathode with robust cyclability for Na ion batteries. Finally, although the crystal overlap Hamilton population does not indicate any significant bonding between oxidized O ions upon desodiation in $\mathrm{N}{\mathrm{a}}_{x}M{\mathrm{O}}_3$ compounds, we predict that gaseous ${\mathrm{O}}_2$ may still develop through thermodynamic decomposition of $\mathrm{N}{\mathrm{a}}_{1}M{\mathrm{O}}_3$ to $\mathrm{N}{\mathrm{a}}_{1}M{\mathrm{O}}_2$ in some compounds.

We investigate the longitudinal and transverse piezoresistance effect in suspended graphene in the ballistic regime. Utilizing parametrized tight-binding Hamiltonian along with Landauer quantum transport formalism, we devise a methodology to evaluate the piezoresistance effect in graphene. We evaluate the longitudinal and transverse gauge factor of graphene along armchair and zigzag directions in the linear elastic limit ($0\%–10\%$). The gauge factors along armchair and zigzag directions are identical. Our model predicts a significant enhancement ($\approx 1000\%$) in the value of transverse gauge factor compared to longitudinal gauge factor along with sign inversion. The calculated value of longitudinal gauge factor is $\approx 0.3,$ whereas the transverse gauge factor is $\approx -3.3$. We rationalize our prediction based on the deformation of Dirac cone and change in separation between transverse modes due to longitudinal and transverse strain. The results obtained herein can serve as a template for high-strain piezoresistance effect of graphene in nanoelectromechanical systems.

Reconfigurable magnetic tunnel diodes and transistors are a new concept in spintronics. The realization of such a device requires the use of materials with unique spin-dependent electronic properties such as half-metallic magnets (HMMs) and spin-gapless semiconductors (SGSs). Quaternary Heusler compounds offer a unique platform to design within the same family of compounds HMMs and SGSs with similar lattice constants to make coherent growth of the consecutive spacers of the device possible. Employing state-of-the-art first-principles calculations, we scan the quaternary Heusler compounds and identify suitable candidates for these spintronic devices combining the desirable properties: (i) HMMs with sizable energy gap or SGSs with spin gaps both below and above the Fermi level, (ii) high Curie temperature, (iii) convex hull energy distance less than 0.20 eV, and (iv) negative formation energies. Our results pave the way for the experimental realization of the proposed magnetic tunnel diodes and transistors.

Room temperature magnetoelectric multiferroic thin films offer great promises for the spintronics industry. The actual development of devices, however, requires the production of ultrathin atomically smooth films of high crystalline quality in order to increase spin transfer efficiency. Using both high-resolution transmission electron microscopy and atomically resolved electron energy loss spectroscopy, we unveil the complex growth mechanism of a promising candidate, gallium ferrite. This material, with its net room-temperature magnetization of approximately $100\mathrm{emu}/\mathrm{c}{\mathrm{m}}^3$, is an interesting challenger to the antiferromagnetic bismuth ferrite. We obtained atomically flat gallium ferrite ultrathin films with a thickness control down to one fourth of a unit cell. Films with thicknesses as low as 7 nm are polar and show a perpendicular magnetic anisotropy of $3\times {10}^3\mathrm{J}/{\mathrm{m}}^3$ at 300 K, which makes them particularly attractive for spin current transmission in spintronic devices, such as spin Hall effect based heavy-metal / ferrimagnetic oxide heterostructures.

Whereas intrinsic defects in silicon carbide (SiC) have been widely considered for qubit applications, transition metals in this material have not yet been recognized as alternative systems. We have investigated the magneto-optical properties of the ${\mathrm{V}}^{3+}$ center in $4H\text{-SiC}$ by electron paramagnetic resonance (EPR) and photo-EPR spectroscopy in view of their possible application in quantum technology. We show that they fulfill all the requirements for such applications: a high-spin $S=1$ ground state, optically induced ground-state spin polarization of more than 70%, long spin-lattice relaxation times of the order of a second, as well as associated zero-phonon photoluminescence emission lines in the range of 1.8 μm. Further, the zero-field splitting parameter $D$ is temperature dependent and increases between $T=4\mathrm{K}$ and $T=292\mathrm{K}$ linearly with a rate of 440 kHz/K, allowing potential nanoscale temperature sensing. These properties make the vanadium acceptor an extremely promising candidate for qubit applications with optical properties in the telecommunication optical range.

Tin(II) containing phosphates, ${\mathrm{Sn}}_n{\mathrm{P}}_2{\mathrm{O}}_{5+n}$ ($n$ is an integer), are promising candidates for $p$-type transparent conductors due to their good stability, suitable band gaps, and reasonable hole effective masses. Here we conduct first-principles calculations on ${\mathrm{Sn}}_n{\mathrm{P}}_2{\mathrm{O}}_{5+n}$ type compounds by exploring their defect properties along with the dopability to find better candidates for $p$-type transparent conducting oxides. We consider two compounds, ${\mathrm{Sn}}_3{\mathrm{P}}_2{\mathrm{O}}_8$ ($n=3$) and ${\mathrm{Sn}}_5{\mathrm{P}}_2{\mathrm{O}}_{10}$ ($n=5$), with their binary counterpart SnO for a thorough comparison. Various likely native defects, as well as possible hydrogen-related extrinsic impurities have been examined. In ${\mathrm{Sn}}_n{\mathrm{P}}_2{\mathrm{O}}_{5+n}$, Sn interstitial and Sn vacancy are the dominant donor and acceptor defects. In contrast to SnO, Sn vacancies have quite deep charge transition levels in ${\mathrm{Sn}}_n{\mathrm{P}}_2{\mathrm{O}}_{5+n}$. The results indicate that both the studied phosphates are not good $p$-type transparent conductors even at the optimal growth conditions. However, our findings suggest that ${\mathrm{Sn}}_n{\mathrm{P}}_2{\mathrm{O}}_{5+n}$ with a higher $n$ would allow for a relatively higher hole concentration and a shallow-level defect for Sn vacancy, thus calling future research in this direction.

The proximity-coupled topological-insulator / superconductor (TI/SC) bilayer system is a representative system to realize topological superconductivity. In order to better understand this unique state and enable future applications of the TI/SC bilayer, a comprehensive characterization and understanding of the microscopic properties of the bilayer are required. In this work, a microwave Meissner screening study, which exploits a high-precision microwave resonator technique, is conducted on the ${\mathrm{SmB}}_6/{\mathrm{YB}}_6$ thin-film bilayers as an example TI/SC system. The study reveals spatially dependent electrodynamic screening response of the TI/SC system that is not accessible to other techniques, from which the corresponding microscopic properties of a TI/SC bilayer can be obtained. The TI thickness dependence of the effective penetration depth suggests the existence of a bulk insulating region in the TI layer. The spatially dependent electrodynamic screening model analysis provides an estimate for the characteristic lengths of the TI/SC bilayer: normal penetration depth, normal coherence length, and the thickness of the surface states.

The organic-inorganic lead-halide perovskites are composed of organic molecules imbedded in an inorganic framework. The compounds with general formula ${\mathrm{CH}}_3{\mathrm{NH}}_3\mathrm{Pb}{X}_3$ ($\mathrm{MAPb}{X}_3$) display large photovoltaic efficiencies for halogens $X=\mathrm{Cl}$, Br, and I in a wide variety of sample geometries and preparation methods. The organic cation and inorganic framework are bound by hydrogen bonds that tether the molecules to the halide anions, and this has been suggested to be important to the optoelectronic properties. We have studied the effects of this bonding using time-of-flight neutron spectroscopy to measure the molecular dynamics in ${\mathrm{CH}}_3{\mathrm{NH}}_3{\mathrm{PbCl}}_3$ (${\mathrm{MAPbCl}}_3$). Low-energy/high-resolution neutron backscattering reveals thermally activated molecular dynamics with a characteristic temperature of $\sim 95$ K. At this same temperature, higher-energy neutron spectroscopy indicates the presence of an anomalous broadening in energy (reduced lifetime) associated with the molecular vibrations. By contrast, neutron powder diffraction shows that a spatially long-range structural phase transitions occurs at 178 K (cubic $\to$ tetragonal) and 173 K (tetragonal $\to$ orthorhombic). The large difference between these two temperature scales suggests that the molecular and inorganic lattice dynamics in ${\mathrm{MAPbCl}}_3$ are actually decoupled. With the assumption that underlying physical mechanisms do not change with differing halogens in the organic-inorganic perovskites, we speculate that the energy scale most relevant to the photovoltaic properties of the lead-halogen perovskites is set by the lead-halide bond, not by the hydrogen bond.

The semiconducting oxide $\beta$-gallium oxide ($\beta -{\mathrm{Ga}}_2{\mathrm{O}}_3$) possesses a monoclinic unit cell, whose low symmetry generally leads to anisotropic physical properties. For example, its electrical conductivity is generally described by a polar symmetrical tensor of second rank consisting of four independent components. Using van der Pauw measurements in a well-defined square geometry on differently oriented high-quality bulk samples and the comparison to finite-element simulations, we precisely determine the ratio of all elements of the $\beta -{\mathrm{Ga}}_2{\mathrm{O}}_3$ three-dimensional electrical conductivity tensor. Despite the strong structural anisotropy, a weakly anisotropic conductivity at and above room temperature was found. In the $a^{*}bc$ coordinate system, the diagonal elements deviate from each other by no more than 6%. Based on these results and the off-diagonal element being $\approx 5\%$ of the diagonal ones, the direction of highest conductivity is rotated ${(59\pm 15)}^{\circ }$ from the $c$ direction towards the $a^{*}$ direction with a conductivity of $(1.12\pm 0.09)\times$ that in the perpendicular direction of lowest conductivity. Analysis of the temperature dependence of the anisotropy and mobility of differently doped samples allows us to compare the anisotropy for dominant phonon scattering to that for dominant ionized-impurity scattering. For both scattering mechanisms, the conductivities along the $a$ and $b$ direction agree within 2%. In contrast, the conductivity along the $c$ direction amounts to $0.96\times$ that along the $b$ direction for dominant phonon scattering, and up to $1.12\times$ for ionized-impurity scattering. The transport anisotropies are determined to be larger than the theoretically predicted effective mass anisotropy, suggesting slightly anisotropic scattering mechanisms. We demonstrate that significantly higher anisotropies can be caused by oriented, extended structural defects in the form of low-angle grain boundaries, for which we determined energy barriers of up to 93 meV.

Magnetism in lanthanum cobaltite (LCO, ${\mathrm{LaCoO}}_3$) appears to be strongly dependent on strain, defects, and nanostructuring. LCO on strontium titanate (STO, ${\mathrm{SrTiO}}_3$) is a ferromagnet with an interesting strain relaxation mechanism that yields a lattice modulation. However, the driving force of the ferromagnetism is still controversial. Experiments debate between a vacancy-driven or strain-driven mechanism for epitaxial LCO's ferromagnetism. We found that a weak lateral modulation of the superstructure is sufficient to promote ferromagnetism. Our research also showed that ferromagnetism appears under uniaxial compression and expansion. Although earlier experiments suggest that bulk LCO is nonmagnetic, our diffusion Monte Carlo calculations found that magnetic phases have a lower energy ground state for bulk LCO. This paper discusses recent experiments indicating a more complicated picture for the bulk magnetism and closer agreement with our calculations. The role of defects are also discussed through excited-state calculations.

We combine droplet epitaxy with low-energy electron microscopy imaging techniques to map the surface phase diagram of GaAs(001). The phase patterns produced in droplet epitaxy are interpreted using a simple model which links the spatial coordinates of phase boundaries to the free energy. It is thereby possible to gain important information on surface phase stability, based on the observed sequential order of the phases away from the droplet edge. This can be used to augment existing $T=0\text{K}$ phase diagrams generated by density-functional theory calculations. We establish the existence of a $(3\times 6)$ phase, and confirm that the controversial $(6\times 6)$ phase is thermodynamically stable over a narrow range of chemical potential.

The pairing mechanism of unconventional superconductivity in strontium titanate is hotly debated. Here, using a multisensor experimental apparatus with a mechanical strain cell, an optical microscope, and with transport and magnetic probes all contained in a closed-cycle dilution refrigerator, we determined that the superconducting transition temperature of strontium titanate increases dramatically even for very small strains induced by application of uniaxial tension. These results imply that superconductivity is controlled by very small atomic shifts; the only strain-sensitive pairing channel candidate is the one linked to quantum ferroelectric (polar) instability. This investigation, therefore, uncovers additional constraints on the debated theories of superconductivity in this low carrier concentration material near the ferroelectric quantum phase transition.

The search for noncentrosymmetric superconductors that may exhibit unusual physical properties and unconventional superconductivity has yielded the synthesis of a noncentrosymmetric phosphide ${\mathrm{Mg}}_2{\mathrm{Rh}}_3\mathrm{P}$ with an $\mathrm{A}{\mathrm{l}}_2\mathrm{M}{\mathrm{o}}_3\mathrm{C}$-type structure. Although stoichiometric ${\mathrm{Mg}}_2{\mathrm{Rh}}_3\mathrm{P}$ does not exhibit superconductivity at temperatures above 2 K, we found that an Mg deficiency of approximately 5 at.% in the ${\mathrm{Mg}}_2{\mathrm{Rh}}_3\mathrm{P}$-induced superconductivity at 3.9 K. Physical properties such as the lattice parameter $a=7.0881\AA$, Sommerfeld constant ${\gamma }_{\mathrm{n}}=5.36\mathrm{mJ}\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{K}}^{-2}$, specific heat jump $\mathrm{\Delta }{C}_{\mathrm{el}}/{\gamma }_{\mathrm{n}}{T}_{\mathrm{c}}=0.72$, electron–phonon coupling constant ${\lambda }_{\mathrm{e}-\mathrm{p}}=0.58$, upper critical field $H_{\mathrm{c}2}\left(0\right)=24.3\mathrm{kOe}$, and pressure effect $d{T}_{\mathrm{c}}/dP=-0.34\mathrm{K}/\mathrm{GPa}$ were measured for the superconducting ${\mathrm{Mg}}_{2-\delta }{\mathrm{Rh}}_3\mathrm{P}$ ($\delta \sim 0.1$). Band-structure calculations indicate that exotic fermions, which are not present in high-energy physics, exist in ${\mathrm{Mg}}_2{\mathrm{Rh}}_3\mathrm{P}$. Since Mg, Rh, and P are the first elements used at each crystal site of $\mathrm{A}{\mathrm{l}}_2\mathrm{M}{\mathrm{o}}_3\mathrm{C}$-type compounds, the discovery of ${\mathrm{Mg}}_2{\mathrm{Rh}}_3\mathrm{P}$ may guide the search for new related materials.

We present the temperature dependence of the electrical resistivity, the magnetic susceptibility, and the specific heat of a high-quality single crystal of ${\mathrm{La}}_3{\mathrm{Co}}_4{\mathrm{Sn}}_{13}$. As opposed to earlier reports on this system, these bulk properties exhibit clear anomalies at the phase transition at $T^{*}=151\left(1\right)$ K, while the present data confirm the second-order character of this transition. X-ray diffraction with synchrotron radiation is used to solve the fourfold superstructure in space group $I{2}_{1}3$ as it exists below $T^{*}$ in the charge-density-wave (CDW) state of ${\mathrm{La}}_3{\mathrm{Co}}_4{\mathrm{Sn}}_{13}$. Unlike conventional CDW systems, we have observed hysteresis between the zero-field-cooled and field-cooled magnetization below the CDW transition. This discrepancy can be attributed to a possible magnetic instability arising out of correlations of Co in the lattice, developing at the CDW transition. The crystal structure shows that any modifications of the electronic state of Co might be due to modified binding characteristics of the Sn atoms comprising the trigonal prismatic coordination of Co, while the coordination of Co itself is hardly changed at the phase transition. The superconducting transition is observed at $T_{\text{sc}}=2.85\left(2\right)$ K. The superconducting energy gap is estimated as 5 K on the basis of the specific heat measured down to 0.1 K. These results suggest that ${\mathrm{La}}_3{\mathrm{Co}}_4{\mathrm{Sn}}_{13}$ is a conventional weak-electron-phonon-coupling superconductor.

$5d$ iridates have shown vast emergent phenomena due to a strong interplay among their lattice, charge, and spin degrees of freedom, because of which the potential in spintronic application of the thin-film form is highly leveraged. Here we have epitaxially stabilized perovskite $\mathrm{SrI}{\mathrm{r}}_{0.8}\mathrm{S}{\mathrm{n}}_{0.2}{\mathrm{O}}_3$ on [001] $\mathrm{SrTi}{\mathrm{O}}_3$ substrates through pulsed laser deposition and systematically characterized the structural, electronic, and magnetic properties. Physical property measurements unravel an insulating ground state with a weak ferromagnetism in the compressively strained epitaxial film. The octahedral rotation pattern is identified by synchrotron x-ray diffraction, resolving a mix of $a^{+}{b}^{-}{c}^{-}$ and $a^{-}{b}^{+}{c}^{-}$ domains. X-ray magnetic resonant scattering directly demonstrates a G-type antiferromagnetic structure of the magnetic order and the spin canting nature of the weak ferromagnetism.

The unexpected properties of a uniaxially expanded TiN bulk arising from increasing the layer spacing from equilibrium are explored using a first-principles approach. We reveal an unusual nonmagnetic-magnetic transition from a TiN bulk to its monolayer. We also investigate the electronic and magnetic structures of a few TiN atomic layers. We find that the bilayer and trilayer, like the TiN bulk, are nonmagnetic poor metals. On the other hand, the monolayer TiN is found to carry a magnetic moment on its Ti atoms, and likely be a semiconductor. The unpaired electron giving rise to magnetism on Ti is primarily in the orbital perpendicular to the layers, and we find it is freed to give rise to magnetism when the layers are slightly separated. We find two different antiferromagnetic states possible on the monolayer, as well as one ferromagnetic, with one of the antiferromagnetic being the lowest energy. The exchange couplings between Ti atoms in such a monolayer are calculated to be antiferromagnetic for both the nearest-neighbor and next-nearest-neighbor sites. We also analyze the binding nature of both the monolayer and bilayer TiN by examining the predominant binding orbitals.

Strain engineering is an important issue in oxide thin films to explore new functionalities. Here a series of high quality epitaxial ${\mathrm{PrVO}}_3$ (PVO) thin films were grown, by pulsed laser deposition (PLD) technique, as a function of thickness on (La,Sr)(Al,Ta)${\mathrm{O}}_3$ (100) [LSAT (100)] and ${\mathrm{LaAlO}}_3$ (100) [LAO (100)] substrates with a nominal lattice mismatch of $-0.8$% and $-2.9$%, respectively. X-ray diffraction revealed a constant out-of-plane lattice parameter of PVO/LSAT with an increase in film thickness, and a rather continuous decrease for PVO/LAO films. Whereas thicker PVO films show a ferromagneticlike behavior, at low thickness a surprising decrease of coercivity ($H_c$) and increase of saturation magnetization ($M_s$) is observed. This behavior is described by using a model of a “dead layer” which possesses a strong paramagnetic susceptibility. Our XPS investigations further reveal the formation of ${\mathrm{V}}^{4+}$ at the surface of the film to be responsible for this paramagnetic dead layer, which is reduced by adding a capping layer on top of the PVO film. Finally, the Néel temperature ($T_N$) is examined as a function of film thickness, and found to vary between 25 and 30 K for LSAT and LAO, respectively. These results pave the way for the use of vanadate in thin film devices.

Chalcopyrite ${\mathrm{CuGaSe}}_2$ has been widely studied as a promising light-harvesting material for solar cells, but new stable phases and compounds with other stoichiometries of the Cu-Ga-Se ternary systems could have more desirable properties and their optoelectronic properties could be engineered by controlling the degree of disorder. Employing an ab initio evolutionary variable-composition search and Monte Carlo simulations based on the special quasirandom structures, we identified several stable phases of ${\mathrm{Cu}}_2\mathrm{Se}$, ${\mathrm{Ga}}_2{\mathrm{Se}}_3$, and their alloys ${\mathrm{CuGaSe}}_2$, ${\mathrm{CuGa}}_3{\mathrm{Se}}_5$, ${\mathrm{CuGa}}_5{\mathrm{Se}}_8$, and ${\mathrm{Cu}}_4{\mathrm{Ga}}_2{\mathrm{Se}}_5$ at ambient and high pressures. Computed electronic band structures of these alloys indicate that they are semiconductors with direct band gaps ranging from 0.77 eV of ${\mathrm{Cu}}_4{\mathrm{Ga}}_2{\mathrm{Se}}_5$ to 2.11 eV of ${\mathrm{CuGa}}_3{\mathrm{Se}}_5$. Our results disclose anomalous changes in band gap induced by varying chemical composition and applying high pressure, due to the variation in $p\text{−}d$ coupling between Se and Cu atoms. Furthermore, the band gap of ${\mathrm{CuGaSe}}_2$ can vary continuously from 1.64 eV for the ordered chalcopyrite structure to 0.23 eV for the fully disordered structure; thus optical absorption spectra in these alloys could be tuned by controlling the synthesis temperature and annealing time, which determine the degree of ordering.

We report the first synthesis of the intermetallic compound ${\mathrm{Ni}}_5{\mathrm{Al}}_3$ in the nanocrystalline form. At the nanometer length scale, a stable ${\mathrm{Ni}}_5{\mathrm{Al}}_3$ compound (core) does not form without a NiO shell. Detailed structural and microstructural characterization as well as the compositional analysis indicate the presence of ${\mathrm{Ni}}_5{\mathrm{Al}}_3/\mathrm{NiO}$ core/shell nanoparticles and log-normal crystallite size distribution with mean size $d\simeq$ 6 nm. “Zero-field” (dc magnetic field, $H=0$) linear (${\chi }_1$) and nonlinear (${\chi }_n$ with $n=2,3,4,5$) ac-magnetic susceptibilities have been measured as functions of temperature at various ac driving field amplitudes over three decades of frequency on the nanocrystalline samples ${\mathrm{S}}_1$ and ${\mathrm{S}}_2$ of composition ${\mathrm{Ni}}_{5+x}{\mathrm{Al}}_{3-x}/\mathrm{NiO}$ ($x=0.014$) and ${\mathrm{Ni}}_{5-x}{\mathrm{Al}}_{3+x}/\mathrm{NiO}$ ($x=0.038$), respectively. ${\chi }_1\left(T\right)$ and ${\chi }_n\left(T\right)$ are shown to provide conclusive evidence for the existence of two spin glass (SG) thermodynamic phase transitions: one at $T_i(H=0)\simeq 138$ K and the other at a lower temperature $T_p(H=0)\simeq 108$ K in both ${\mathrm{S}}_1$ and ${\mathrm{S}}_2$. Linear ac-susceptibility in superposed dc magnetic fields demonstrates that the thermodynamic nature of these transitions is preserved in finite fields and the $H-T$ phase diagrams for the samples ${\mathrm{S}}_1$ and ${\mathrm{S}}_2$ conform very well only with the $H-T$ phase diagram predicted by the chirality-driven spin glass (SG) ordering model for a three-dimensional nearest-neighbor Heisenberg SG system with weak random anisotropy. A detailed comparison between theory and experiment permits us to unambiguously identify various “zero-field” and “in-field” SG phase transitions as (i) the simultaneous paramagnetic (PM): chiral-spin glass (CG) and PM-SG phase transitions at $T_i\left(H\right)$ and (ii) the replica symmetry-breaking SG transition at $T_p\left(H\right)$.

$\mathrm{SrTi}{\mathrm{O}}_3$ thin films were grown on ${}^{18}\mathrm{O}$-exchanged $\mathrm{SrTi}{\mathrm{O}}_3$ single crystalline substrates by pulsed-laser deposition, rf sputtering, and oxide molecular-beam epitaxy to study their oxygen diffusion depth profiles using secondary ion mass spectrometry and elastic recoil detection analysis depth profiling. The oxygen depth profiling shows that $\mathrm{SrTi}{\mathrm{O}}_3$ films prepared with the three different deposition techniques will take oxygen from the substrate, even at room temperature. This confirms that the substrate is one possible oxygen source for the growth of oxide thin films independent of the physical vapor deposition technique employed. It was also found that a reactive oxygen environment changes the oxygen composition of the substrate during the growth of a film and partly replaces ${}^{18}\mathrm{O}$ with ${}^{16}\mathrm{O}$ up to a depth of several tens of nm. These findings imply that $\mathrm{SrTi}{\mathrm{O}}_3$ and therefore other ion conducting oxide substrates, which are commonly used as platforms for thin film growth, can be considered capricious in nature with respect to oxygen chemistry and lattice constants.