We have obtained and analyzed the optical transmission spectra of diamond-like carbon films deposited on quartz substrates by pulsed laser deposition (λ = 1064 nm, τ = 20 nsec, q = 4.9⋅10 8 W/cm 2 ) under vacuum . Based on the spectra obtained, we have estimated the size of the bandgap by the Tauc method, and also have studied the growth dynamics of the coatings formed.Introduction. Due to the increasing interest in diamond electronics, diamond-like carbon films have been the subject of intensive study for several decades. Using diamond-like carbon nanostructures instead of the silicon type can result in creation of chips with a higher concentration of transistors, since diamond has high thermal conductivity and heat resistance (sublimation temperature above 3000 K [1]). In addition, diamond-like carbon films are chemically inert and extremely strong.Recently, increasing attention has been focused on synthesis and study of diamond-like carbon films of different structures (amorphous, crystalline, having different ratios of sp 2 and sp 3 carbon bonds, etc.) [2, 3] and different compositions (containing hydrogen, nitrogen, and other elements) [4]. Efficient methods have been found for doping diamond-like carbon films with boron to obtain p-type conductivity in them [5].Laser spraying of carbon films provides greater opportunities for obtaining new materials with unusual properties. In deposition of these materials, a large role is played by the stored energy of the particles of the carbon plasma, under the action of which new, promising structural forms are obtained (tetrahedral carbon, nanocrystalline carbon, etc.). The laser method has an advantage over other methods for depositing thin films, since when coatings are deposited by this method, it is easier to monitor the production conditions for obtaining the deposited coating. Furthermore, laser radiation itself is "sterile" [6].Vacuum deposition of films is the most widely used and universal method for obtaining thin-film structures for broadest application (including complicated applications) in production of active film semiconductor structures (p-n junctions) [7].The main problem during deposition is to obtain films having properties which most fully correspond to their area of application. Very often we need to obtain films with high optical transparency, and in addition we can determine other parameters of the film from the spectral characteristics.The aim of this work was to determine the optical bandgap and also to study the effect of the deposition parameters on the optical properties of diamond-like carbon films.The Experiment. The schematic diagram for the experimental system is shown in Fig. 1. For deposition of diamond-like carbon films, we used an LS-2137 YAG:Nd 3+ laser (Lotis TII) with repetition frequency 5 Hz for the laser pulses, wavelength λ = 1064 nm, and pulse length τ = 20 nsec. The laser pulse energy was detected using an IMO-3 power meter. To do this, some of the laser radiation was diverted to the measurement head by means of a 10% beam...
We have used Raman light scattering and electron paramagnetic resonance methods to study carbon films obtained by laser plasma deposition, using different types of graphite targets. We have established that the films deposited in this way have a diamond-like structure and are a nanostructured composite containing clusters of both sp 2 and sp 3 -hybridized carbon. We have shown that an increase in structural perfection of the graphite target causes an improvement in the structure of the carbon films obtained from it and an increase in the content of sp 3 -hybridized carbon in it. Thermal stimulation of the substrate during application of a coating leads to the same effect.Introduction. Today there is significant interest in development of technologies for deposition of thin carbon films on various materials. Among the known methods for deposition of such films, an important position is occupied by the method of deposition from a laser ablation plasma under vacuum [1]. Its indisputable advantages include the lack of impurities in the deposited coatings (less than 1%) [2], the relatively easy variation of the deposition parameters (energetics, wavelength of the radiation), the high degree of monitoring of the deposition process (scanning the target with a laser beam, excitation of the substrate), and also the significant content of sp 3 phase in the deposited coatings [3]. Using the laser plasma deposition method, it is possible to obtain various carbon coatings whose structure is determined as nanocrystalline graphite, amorphous carbon, tetrahedral carbon, glassy carbon, metallized carbon, etc.Nevertheless, to date there has been no complete model describing the processes occurring in laser plasma deposition of carbon films. The question of the effect of the deposition conditions on the structure of the coatings obtained is also not completely clear. Most authors have paid special attention to a parameter such as the power density of the laser radiation. In [4,5], it was shown that the fraction of sp 3 -bonded carbon in the films increased as the power density of the laser radiation increased up to 3.7⋅10 8 W/cm 2 . For high power densities, we observe an appreciable decrease in the amount of sp 3 -bonded carbon [5]. In [6], on the other hand, transition from a structure with predominantly sp 2 bonds to a structure with predominantly sp 3 bonds was observed for a power density of ~3⋅10 8 W/cm 2 . Further increase in the power density led to an increase in the fraction of sp 3 -bonded carbon, all the way up to 80%. Despite the difference between the dependences obtained, the authors of all the indicated papers relate the increase in the concentration of sp 3 -bonded carbon when the power density of the laser radiation increases to the increase in the degree of ionization of the carbon plasma as a result of the increase in its temperature. The authors of [5] related the increase in the amount of sp 2 -bonded carbon observed for high power densities to disordering of sp 3 clusters when exposed to particles of the carb...
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