E. V. Skorokhodov

Ferromagnetic resonance in interacting magnetic microstrips

The results of the micromagnetic simulation of forced oscillations of the magnetization in a system of two interacting microstrips located at an angle to each other have been presented. The ferromagnetic resonance spectra and the mode composition of resonant oscillations of the system have been investigated under the conditions of magnetostatic and exchange interactions between the microstrips. It has been shown that the magnetostatic interaction leads to the possibility of the excitation of in-phase and out-of-phase coupled oscillations of the magnetization of the microstrips. In the systems of exchange-coupled microstrips, there are intense resonances due to oscillations of the domain walls. The transformation of the ferromagnetic resonance spectrum and the change in the mode composition of resonant oscillations in different equilibrium configurations of the magnetization of the system have been discussed, as well as the conditions for the excitation of oscillations of different types depending on the direction of the microwave magnetic field.

Chemically amplified resists for high-resolution lithography

Chemically amplified resists based on methyl methacrylate ter-copolymers with methacrylic acid and isobornyl (met)acrylates, experiencing hydrolysis in the presence of photogenerated acid, responsible for pattern generation in resists, when they are exposed to the deep ultraviolet (254 nm), extreme ultraviolet (13.5 nm), and electron beam, are studied. The influence of the polymeric matrix, photoacid generator, and exposure conditions on quality of the chemically amplified image is evaluated.

Effect of Polymer Matrix and Photoacid Generator on the Lithographic Properties of Chemically Amplified Photoresist

Resistive compositions based on ter-copolymers of isobornylacrylate with methylmethacrylate and (meth)acrylic acid, which are synthesized using the controlled radical polymerization with reversible chain transfer, as well as triphenylsulphoniumtriflate as a photo-sensitive catalyst are studied. The effect of the chain-transfer agent, as well as the composition and molecular weight of the copolymer on the sensitivity of the resists to UV radiation (222 nm), is determined. Using the ter-copolymer of tert-butoxycarbonyloxystyrene with methylmethacrylate and methacrylic acid, the dependence of the lithographic properties of the photoresist on the chemical composition of the photoacid generator is analyzed. The plasma-chemical stability of (co)polymer resists of methacrylic series in the plasma of Ar + SF6 is studied.

Influence of the microcrystalline structure on the magnetic properties of ferromagnetic films and structures on their base

This paper presents the results of investigating the crystal structure of thin films of the Co40Fe60 composition obtained by magnetron sputtering on their magnetic properties and properties of ferromagnetic nanostructures formed from these films using the optical and electron lithography. It has been found experimentally that magnetic properties of the structures depend on the crystalline-grain sizes, which can be controlled by means of deposition of additional buffer layers of various materials ∼1 nm thick on the substrate under the ferromagnetic film. It has been shown that the crystallite size can be the main factor that determines the minimal lateral sizes of the structures with specified magnetic properties, which are formed from thin ferromagnetic films.

Magnetostatic interaction effects in an ordering hexagonal array of ferromagnetic nanoparticles

The results from investigating magnetostatic interaction effects in ordered hexagonal arrays of anisotropic single-domain ferromagnetic nanoparticles are presented. It is demonstrated theoretically and experimentally that two stable states (with quasi-uniform configurations of magnetic moments and with zero averaged magnetic moment configurations) can be easily attained in such arrays. It is shown that the structure of an ferromagnetic resonance spectrum depends strongly on the extent of magnetostatic interaction and the spatial configuration of the magnetic moments in the array.

Domain wall pinning controlled by the magnetic field of four nanoparticles in a ferromagnetic nanowire

This paper presents the results of theoretical and experimental investigations of the domain wall pinning in a planar ferromagnetic system consisting of a nanowire and four rectangular uniformly magnetized nanoparticles located at an angle to the nanowire axis. Based on the calculations of the interaction energy of the domain wall with stray fields of nanoparticles and the micromagnetic simulation, it has been demonstrated that, in this system, there are different variants of the domain wall pinning, which are determined by the relative orientation of the magnetic moments of nanoparticles and the magnetization of the nanowire. The possibility of the creation of magnetic logic cells based on the structures under consideration has been discussed.

Reflective mask for projection lithography operating at a wavelength of 13.5 nm

This work is devoted to the technology of mask manufacturing and investigation of the characteristics of the reflective mask employed in the extreme ultraviolet lithography test bench designed at the Institute for Physics of Microstructures, Russian Academy of Sciences. The mask’s structure and composition have been optimized. The antireflecting (absorbing) coating and stop-layer materials that are used to etch the mask structure and the multilayer interference system, which reflects radiation at the operating wavelength, have been selected. The mask manufacturing technology is described. The measured reflective and geometrical characteristics of a mask (absorbing layer thicknesses, line widths, and line-edge roughnesses) are presented. A new direct method for certifying mask defects of 30 nm or more is proposed.

Influence of the Chemical Structure of (Co)Polymer Resists on Their Sensitivity to Radiation

Resists operating via two mechanisms, i.e., disruption of the main chain and hydrolysis of side functional groups occurring upon EUV and electron beam irradiation, are studied as a function of the chemical composition of a polymer substrate. We show that the latter, belonging to the group of chemically amplified resists, are an order of magnitude more sensitive to radiation and possess outstanding contrast, as compared with disruptive type resists.

Magnetic Resonance Force Microscopy of a Permalloy Microstrip Array

The ferromagnetic resonance in an array of permalloy microstrips 3000 × 500 × 30 nm in size ordered on a rectangular grid 3.5 × 6 μm in size has been investigated by magnetic resonance force microscopy. The dependences of magnetic resonance force microscopy spectra of a sample on the probe–sample distance are analyzed. The possibility of detection of a ferromagnetic resonance spectrum of a single microstrip is demonstrated.

Magnetic Skyrmions in Thickness-Modulated Films

The possibility of the formation of lattices of magnetic skyrmions in thickness-modulated films with perpendicular magnetic anisotropy has been studied experimentally. The samples constitute a regular rectangular lattice (300 nm in period) of cylindrical bulges (150 nm in diameter) formed in a Co/Pt multilayer film by electron lithography. The spatial symmetry of a magnetic force microscopy signal indicates the formation of magnetic skyrmions in the process of remagnetization of the system. Formed skyrmions remain stable in the absence of an external magnetic field. The experimental data are in good agreement with the numerical micromagnetic simulation of the system.