0000000000180174
AUTHOR
Andrejs Petruhins
Modeling of kinetic and static friction between an elastically bent nanowire and a flat surface
Friction forces for a nanowire (NW) elastically bent on flat substrate were investigated both theoretically and experimentally. Models based on elastic beam theory were proposed considering balance of external, frictional, and elastic forces along the NW. The distributed friction force was determined for two cases: (i) the NW was uniformly dragged at its midpoint and bent by kinetic friction forces and (ii) the NW was held in a bent state by static friction forces. The first case considers a uniform distribution of kinetic friction along the NW and enables the measurement of the friction force from the elastically deformed NW profile. The second case exploits the interplay between static fr…
Investigation of temperature dependence of magnetic properties of Cr$_2$O$_3$ thin film structure using a magnetic field imaging technique based on Nitrogen-Vacancy centres in diamond crystal
This work presents a magnetic field imaging method based on color centres in diamond crystal applied to thin film structure. To demonstrate the capacity of our device we have used it for characterization of magnetic properties in microscopic scale of Cr$_2$O$_3$ thin film structure above and below N\'eel temperature. The obtained measurement results clearly identify the detection of the magnetic phase transition of Cr$_2$O$_3$ thin film with an unexpected diamagnetic like behaviour at 19$^{\circ}$C (below the N\'eel temperature of Cr$_2$O$_3$). To have better insights in the magnetic fields created by the thin films we present simulations of the magnetic fields near the thin film surface. W…
Some aspects of pulsed laser deposition of Si nanocrystalline films
International audience; Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed.
Detection of magnetic thin film impurity phases using nitrogen vacancy centers in diamond crystal
We demonstrate the possibility to detect magnetic impurity phases in thin films using magnetic field imaging technique based on a layer of nitrogen-vacancy centers in the diamond lattice. We demonstrate results of magnetic field distributions created by impurity phases as well as mechanical defects on the thin film surface.
Lāzerablācijā iegūtu pusvadītāju nanokristālu īpašības
ZnO un nanokristāliskā Si plānās kārtiņas tika iegūtas izmantojot pikosekunžu impulsu lāzera ablācijas metodi vakuumā uz pamatnes pie istabas temperatūras kā arī pētītas iegūto kārtiņu īpašības. ZnO paraugiem tika veikta pēcapstrāde apdedzinot to vakuumā un gaisā pie 600° C temperatūras un tika pētīta apdedzināšanas ietekme uz optisko absorbciju, fotoluminiscenci un elektriskajām īpašībām. Tika iegūtas arī ar alumīniju leģētas cinka oksīda plānā kārtiņa un pētītas tās optiskā absorbcija un elektriskā vadītspēja. Si plānajām kārtiņām ar atomspēku mikroskopu tika novērota nanokristāliskā struktūra, kuru apstiprina arī Ramana un optiskās absorbcijas spektri. Tika novērota absorbcijas malas nob…
Surface magnetic structure investigation of a nanolaminated Mn$_2$GaC thin film using a magnetic field microscope based on Nitrogen-Vacancy centers
This work presents a magnetic field imaging method based on color centers in diamond crystal applied to a thin film of a nanolaminated Mn$_2$GaC MAX phase. Magnetic properties of the surface related structures have been described around the first order transition at 214 K by performing measurements in the temperature range between 200 K and 235 K with the surface features fading out by increasing temperature above the transition temperature. The results presented here demonstrate how Nitrogen-Vacancy center based magnetic microscopy can supplement the traditionally used set of experimental techniques, giving additional information of microscopic scale magnetic field features, and allowing t…
Characterization of microscopic ferromagnetic defects in thin films using magnetic microscope based on Nitrogen-Vacancy centres
In this work we present results acquired by applying magnetic field imaging technique based on Nitrogen-Vacancy centres in diamond crystal for characterization of magnetic thin films defects. We used the constructed wide-field magnetic microscope for measurements of two kinds of magnetic defects in thin films. One family of defects under study was a result of non-optimal thin film growth conditions. The magnetic field maps of several regions of the thin films created under very similar conditions to previously published research revealed microscopic impurity islands of ferromagnetic defects, that potentially could disturb the magnetic properties of the surface. The second part of the measur…