Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStrain in epitaxial MnSi films on Si(111) in the thick film limit studied by polarization-dependent extended x-ray absorption fine structure
107
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report a study of the strain state of epitaxial MnSi films on Si(111) substrates in the thick film limit (100-500~AA) as a function of film thickness using polarization-dependent extended x-ray absorption fine structure (EXAFS). All films investigated are phase-pure and of high quality with a sharp interface between MnSi and Si. The investigated MnSi films are in a thickness regime where the magnetic transition temperature $T_mathrm{c}$ assumes a thickness-independent enhanced value of $geq$43~K as compared with that of bulk MnSi, where $T_mathrm{c} approx 29~{rm K}$. A detailed refinement of the EXAFS data reveals that the Mn positions are unchanged, whereas the Si positions vary along the out-of-plane [111]-direction, alternating in orientation from unit cell to unit cell. Thus, for thick MnSi films, the unit cell volume is essentially that of bulk MnSi --- except in the vicinity of the interface with the Si substrate (thin film limit). In view of the enhanced magnetic transition temperature we conclude that the mere presence of the interface, and its specific characteristics, strongly affects the magnetic properties of the entire MnSi film, even far from the interface. Our analysis provides invaluable information about the local strain at the MnSi/Si(111) interface. The presented methodology of polarization dependent EXAFS can also be employed to investigate the local structure of other interesting interfaces.
rate research
Read More
The structural properties of Er-doped AlNO epilayers grown by radio frequency magnetron sputtering were studied by Extended X-ray Absorption Fine Structure (EXAFS) spectra recorded at the Er L 3 edge. The analysis revealed that Er substitutes for Al in all the studied samples and the increase in Er concentration from 0.5 to 3.6 at.% is not accompanied by formation of ErN, Er 2 O 3 or Er clusters. Simultaneously recorded X-ray Absorption Near Edge Structure (XANES) spectra verify that the bonding configuration of Er is similar in all studied samples. The Er-N distance is 2 constant at 2.18-2.19 {AA} i.e. approximately 15% larger than the Al-N bondlength, revealing that the introduction of Er in the cation sublattice causes considerable local distortion. The Debye-Waller factor, which measures the static disorder, of the second nearest shell of Al neighbors, has a local minimum for the sample containing 1% Er that coincides with the highest photoluminescence efficiency of the sample set.
We have studied in-gap states in epitaxial CoFe2O4(111), which potentially acts as a perfect spin filter, grown on a Al2O3(111)/Si(111) structure by using ellipsometry, Fe L2,3-edge x-ray absorption spectroscopy (XAS), and Fe L2,3-edge resonant inelastic x-ray scattering (RIXS), and revealed the relation between the in-gap states and chemical defects due to the Fe2+ cations at the octahedral sites (Fe2+ (Oh) cations). The ellipsometry measurements showed the indirect band gap of 1.24 eV for the CoFe2O4 layer and the Fe L2,3-edge XAS confirmed the characteristic photon energy for the preferential excitation of the Fe2+ (Oh) cations. In the Fe L3-edge RIXS spectra, a band-gap excitation and an excitation whose energy is smaller than the band-gap energy (Eg = 1.24 eV) of CoF2O4, which we refer to as below-band-gap excitation (BBGE) hereafter, were observed. The intensity of the BBGE was strengthened at the preferential excitation energy of the Fe2+ (Oh) cations. In addition, the intensity of the BBGE was significantly increased when the thickness of the CoFe2O4 layer was decreased from 11 to 1.4 nm, which coincides with the increase in the site occupancy of the Fe2+ (Oh) cations with decreasing the thickness. These results indicate that the BBGE comes from the in-gap states of the Fe2+ (Oh) cations whose density increases near the heterointerface on the bottom Al2O3 layer. We have demonstrated that RIXS measurements and analyses in combination with ellipsometry and XAS are effective to provide an insight into in-gap states in thin-film oxide heterostructures.
We applied soft X-ray absorption spectroscopy to study the Ti L-edge in ferroelectric capacitors using a modified total electron yield method. The inner photo currents and the X-ray absorption spectra were polarization state dependent. The results are explained on the basis of photo electric effects and the inner potential in the ferroelectric capacitors as a result of back-to-back Schottky barriers superimposed by the potential due to the depolarization field. In general, the presented method offers the opportunity to investigate the electronic structure of buried metal-insulator and metal-semiconductor interfaces in thin film devices. Corresponding author: [email protected]
Ferroelectric BaTiO3 films with large polarization have been integrated with Si(001) by pulsed laser deposition. High quality c-oriented epitaxial films are obtained in a substrate temperature range of about 300 deg C wide. The deposition temperature critically affects the growth kinetics and thermodynamics balance, resulting on a high impact in the strain of the BaTiO3 polar axis, which can exceed 2% in films thicker than 100 nm. The ferroelectric polarization scales with the strain and therefore deposition temperature can be used as an efficient tool to tailor ferroelectric polarization. The developed strategy overcomes the main limitations of the conventional strain engineering methodologies based on substrate selection: it can be applied to films on specific substrates including Si(001) and perovskites, and it is not restricted to ultrathin films.
We report experimental and theoretical evidence for the formation of chiral bobbers - an interfacial topological spin texture - in FeGe films grown by molecular beam epitaxy (MBE). After establishing the presence of skyrmions in FeGe/Si(111) thin film samples through Lorentz transmission electron microscopy and topological Hall effect, we perform magnetization measurements that reveal an inverse relationship between film thickness and the slope of the susceptibility (dc{hi}/dH). We present evidence for the evolution as a function of film thickness, L, from a skyrmion phase for L < LD/2 to a cone phase with chiral bobbers at the interface for L > LD/2, where LD ~ 70 nm is the FeGe pitch length. We show using micromagnetic simulations that chiral bobbers, earlier predicted to be metastable, are in fact the stable ground state in the presence of an additional interfacial Rashba Dzyaloshinskii-Moriya interaction (DMI).
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
