Vitaly Ivanovich Konov

1. Diamond is one of the most important materials in modern science and technology because of its unique combination of physical and chemical properties. It possesses the highest thermal conductivi...

Interdigitated diamond photoconductive antennas (IPCAs) with buried pin-type graphitized electrodes have been produced and tested. Each electrode was an array of interconnected parallel pins, which were formed inside N-doped HPHT diamond by 3D laser writing with fs or ns pulses due to local diamond-graphite phase transition. IPCAs differed in the pin period, which varied from 50 to 300 µm, whereas an interelectrode distance was the same (300 µm) in all cases. Increase in the pin period caused decrease in the IPCA efficiency due to transformation of the electric field between the electrodes. Influence of the pin period was clarified via the computer modeling included electrostatic and electrodynamic solutions. Optimization of the electrode parameters has made possible to increase the maximum fluence of THz pulse up to 0.5 µJ/cm2 at the electric field strength 60 kV/cm inside diamond.

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Алмаз, широкозонный радиационно-стойкий полупроводник, перспективен для создания детекторов УФ излучения, в том числе «солнечно-слепых». Реализован вариант полностью углеродного УФ-детектора на монокристальной пластине CVD алмаза со встречно-штыревыми электродами в виде системы мелких (приповерхностных) и глубоких графитизированных канавок, полученных лазерной абляцией без применения литографии. Моделирование распределения электрического поля в детекторе показало преимущество использования заглубленных электродов, которые обеспечивают более однородное распределение поля в кристалле. Спектры фоточувствительности демонстрируют острый максимум в области длин волн 220 нм, причем для заглубленных электродов амплитуда отклика на 75% выше (14 А /Вт).

It is recommended to use high-speed milling to maintain an effective material removal rate and the required cutting-edge geometry. However, on the other hand, high speed increases wear, so the surface of the cutters is modified by deposition functional coatings. The wear of end mills made of CTS12D and H10F tungsten carbides during the high-speed processing of aluminum A97075 (B95T1) was compared. To increase the durability of the tools, well-proven technologies for deposition diamond-like and polycrystalline diamond coatings in microwave plasma with different film structures, which were determined by the coating growth conditions, were used. The milling cutter corner was mostly worn out, but the nature of the wear had its characteristics. It was revealed that at a forced cutting mode of about 1000 m/min, cutters made of CTS12D alloy with a nanocrystalline diamond coating with a “cauliflower” structure and with a diamond-like film showed 10% higher resistance. The primary wear mechanism was adhesive. Images of worn cutting edges were obtained using a 3D optical digital image processing system.

A possibility of laser printing of graphene nanoribbon pixels while preserving the integrity of the structure and shape on the silicon substrate in accordance with the irradiated laser spot is demonstrated. To provide the transfer, a target consisting of a transparent sapphire plate and an absorbing thin titanium film (500 nm thick) coated with a film consisting of graphene nanoribbons is irradiated with a KrF excimer laser (λ=248 nm, τ=20 ns). Optimal conditions for laser irradiation are determined and a technique is developed for transferring a carbon nanomaterial from a growth nickel surface to a titanium film aimed at creating stronger bonds between the nanoribbons. Raman spectroscopy confirms the preservation of structural features of the synthesized atomically precise 7-atoms-wide graphene nanoribbons with an armchair edge during laser transfer.

Numerical modeling of the propagation of high-power femtosecond laser beams in a diamond crystal in the self-focusing mode is carried out. The wavelength of the modeled beams is varied in a wide range (400 nm, 532 nm, 800 nm, and 1064 nm), which covers the most common ultrashort laser systems. For all the wavelengths analyzed, a limitation in the growth of laser energy density inside the diamond crystal with increasing pulse energy is found. This effect has a certain similarity to the effect of optical limitation in laser filaments, but manifests itself outside the filament formation zone and is capable of equalizing the laser energy density, as well as the electron density, inside the extensive pre-focal region.

Diamond is a promising material for terahertz applications. In this work, we use a non-invasive optical pump–terahertz probe method to experimentally study the photoinduced carrier dynamics in doped diamond monocrystals and a new diamond-silicon composite. The chemical vapor deposited diamond substrate with embedded silicon microparticles showed two photoinduced carrier lifetimes (short lifetime on the order of 4 ps and long lifetime on the order of 200 ps). The short lifetime is several times less than in boron-doped diamonds and nitrogen-doped diamonds which were grown using a high temperature–high pressure technique. The observed phenomenon is explained by the transport of photoexcited carriers across the silicon–diamond interface, resulting in dual relaxation dynamics. The observed phenomenon could be used for ultrafast flexible terahertz modulation.

Conductive graphitized grooves on the dielectric surface of diamond have been created by KrF excimer laser radiation. The advantages of such a circuit board in high-field applications is rather limited because the crystal surface has a relatively low electrical breakdown threshold. To increase the electrical strength, a method of encapsulating surface conductive graphitized structures by chemical vapor deposition of an epitaxial diamond layer has been proposed and realized. The quality of the growth diamond is proved by Raman spectroscopy. A comparative study of the electrical resistivity of graphitized wires and the breakdown fields between them before and after diamond growth was carried out. The proposed technique is crucial for diamond-based high-field electro-optical devices, such as THz photoconductive emitters.

We develop a method for the laser synthesis and deposition of carbon–gold films formed by a net of linear sp-carbon chains and stabilized by gold nanoparticles. The originality of the method is in the simultaneous production of carbon chains and gold nanoparticles due to the laser fragmentation of the amorphous carbon and hydrogen tetrachloroaurate (III) or chloroauric acid. We study how surface resistivity alters the effect of the obtained films via the illumination in the visible spectral range.