Nano-Thin Oxide Layers Formed on Hydrogen Plasma Modified Crystalline Si for Advanced Applications

Heat treatment in hydrogen gas and plasma for transparent conducting oxide films such as ZnO, SnO 2 and indium tin oxide

Amorphous hydrogenated silicon–carbon (a-Si:C:H) films were produced by atomic hydrogen–induced (AH) CVD using hexamethyldisilane (HMDS) as a single-source precursor. Radio frequency (rf) hydrogen plasma was the source of atomic hydrogen. The effect of substrate temperature (Ts) on the chemical structure, composition, surface morphology, mechanical properties (dynamic hardness, total stress), and optical properties (refractive index, optical bandgap) of a-Si:C:H film has been examined. Fourier transform infrared (FTIR) spectroscopy and Auger electron spectroscopy (AES) data revealed a drastic drop in hydrogen content in the film, and a rise of the atomic concentration ratio Si/C with increasing Ts, thus accounting for the elimination of organic moieties from the film and the formation of a Si–carbidic structure. In the light of scanning electron microscopy (SEM) and atomic force microscopy (AFM) examinations, the films were found to be morphologically homogeneous materials with a maximum size of surface roughness not exceeding 2 nm at Ts = 300 °C. Both hardness and stress (tensile in nature) are strongly affected by the film composition, their values increasing with rising atomic ratio Si/C. The investigated optical properties of a-Si:C:H film, i.e., refractive index (n) and optical bandgap (E0), can be controlled by the atomic ratio Si/C for a wide range of values: n = 1.58–2.02 and E0 = 2.3–3.2 eV.

Amorphous hydrogenated silicon–carbon (a-Si:C:H) films were produced by atomic hydrogen–induced (AH) CVD using hexamethyldisilane (HMDS) as a single-source precursor. Radio frequency (rf) hydrogen plasma was the source of atomic hydrogen. The effect of substrate temperature (Ts) on the chemical structure, composition, surface morphology, mechanical properties (dynamic hardness, total stress), and optical properties (refractive index, optical bandgap) of a-Si:C:H film has been examined. Fourier transform infrared (FTIR) spectroscopy and Auger electron spectroscopy (AES) data revealed a drastic drop in hydrogen content in the film, and a rise of the atomic concentration ratio Si/C with increasing Ts, thus accounting for the elimination of organic moieties from the film and the formation of a Si–carbidic structure. In the light of scanning electron microscopy (SEM) and atomic force microscopy (AFM) examinations, the films were found to be morphologically homogeneous materials with a maximum size of surface roughness not exceeding 2 nm at Ts = 300 °C. Both hardness and stress (tensile in nature) are strongly affected by the film composition, their values increasing with rising atomic ratio Si/C. The investigated optical properties of a-Si:C:H film, i.e., refractive index (n) and optical bandgap (E0), can be controlled by the atomic ratio Si/C for a wide range of values: n = 1.58–2.02 and E0 = 2.3–3.2 eV.

The structure of the H-related complexes in p-type InP and in liquid encapsulated Czochralski semi-insulating InP:Fe has been studied from the vibrational absorption of their PH stretching modes. The acceptor complexes are produced by plasma hydrogenation so that PD modes have been investigated also. The study has first been performed at 6 K on the fundamentals and on the most intense of the first overtones. The trends in the frequencies and widths of the PH modes of the H-acceptor complexes for Be, Zn, and Cd acceptors are discussed and explained qualitatively. In InP:Fe, the PH intrinsic modes are sharper than those of the acceptor complexes indicating a weaker interaction with the environment. This study has been followed by the measurement of the temperature dependence of the frequencies and of the linewidths for increasing temperatures. The frequency shifts and the broadenings of the lines are interpreted by the temperature-dependent random dephasing of the vibration of the high-frequency oscillators in the excited state. The analysis shows that the PH mode in the acceptor complexes couples to TA phonons of the InP lattice while the one in the complexes involving a vacancy couples to a two TA phonon combination. The anharmonicity of the P-H bonds is comparable to the one in phosphine. A comparison of the anharmonicity parameters derived from the overtone measurements with those derived from the hydrogen isotope effects gives evidence of the interaction between the H atom and the lattice.The amplitude of vibration of the D atom is smaller than that of the H atom and this explains why the interaction of the D atom with the lattice is smaller. This is the reason why the width of the PD modes is smaller than that of the corresponding PH modes. The splitting of some of the PH lines in samples subjected to a uniaxial stress has been studied. The splitting of the PH;Zn mode is in full agreement with a P-H bond along a 〈111〉 axis. The same 〈111〉 orientation of the P-H bond is also found from the splitting of a line attributed to an In vacancy ``decorated'' by a H atom (${\mathit{V}}_{\mathrm{In}}$(PH)). The splitting of the strongest line in InP:Fe leads to its attribution to a PH mode in a cubic center containing four H atoms (${\mathit{V}}_{\mathrm{In}}$(PH${)}_{4}$). The presence of this center seems to account for most of the hydrogen present in InP:Fe. Upon annealing of the InP:Fe samples, ${\mathit{V}}_{\mathrm{In}}$(PH${)}_{4}$ is a source of atomic hydrogen that can be trapped by other defects and it can leave partially hydrogenated In vacancies.

Novel single block process facility including UV excilamp and sources of atomic hydrogen is described. Circular sealed-off KrCl* excilamp emitting two intensive bands at 195 and 222 nm was used. The source of atomic hydrogen on the base of reflecting Penning arc discharge was placed in line with the lamp. Semiconducting structures were treated in an expanding effusion jet of atomic hydrogen. The possibility to realize the process of cleaning GaAs surface under joint action of atomic hydrogen and UV radiation has been investigated. Effect of UV radiation on the rate of removing oxide layer is found at low temperature (18 - 100 degree(s)C). The mechanism providing an explanation for this event is suggested. The possibility to realize GaAs surface cleaning using successive performing the procedures of the surface treatment by atomic hydrogen, its oxidation with UV- stimulation and additional treatment by atomic hydrogen was also studied. The sources of atomic hydrogen and UV radiation developed allows to improve cleaning control and provides a way of producing the surface with specified properties.

One of the unsolved problems in pipeline transport is the insufficient study of the phenomenon of stress corrosion cracking, which is often observed at the main gas pipelines and practically does not appear at the main oil pipelines, despite the fact that these pipelines are built according to same construction standards, practically from the same pipes, are operated under close conditions. Firstly, it does not allow to find effective methods against cracking at main gas pipelines, and secondly, it does not give an opportunity to answer the important question whether further development of corrosion cracking at main oil pipelines should be feared in the future. Aims and Objectives The article poses a problem on the basis of analysis of various manifestations of pipe cracking, the study of known features and regularities, to find the mechanisms for the development of this phenomenon, to construct its physical model, and on its basis to try to answer the question posed. Results A physical model of stress corrosion cracking of underground pipelines has been developed, which makes it possible to explain all observed regularities of this type of destruction. The model is based on the determining role of hydrogen, indicates possible sources of hydrogen on underground pipelines, the patterns of interaction of hydrogen with the pipeline metal, shows the causes of increased internal stresses and cracking of the wall. According to this model, stress corrosion cracking occurs successively in several stages. The first stage is the latent period of development, when there is no cracking yet, but inside the metal of the pipes there are significant changes: the growth of internal stresses due to the accumulation of gas molecules H2 and CH4 at grain boundaries of the crystal structure. At the same time, structural changes occur in the crystals, decarburization and growth of the grains. The second stage - the birth of microcracks, their growth and integration into macrocracks. This is facilitated by stresses caused by working pressure and external forces. One of the components of external forces - the reaction of the soil, which is particularly important in areas with complex uneven terrain. The third stage is the growth of macrocracks before the destruction of the pipeline. Before the completion of the first stage, the remaining stages can not occur. In this lie the answers to the questions posed, as well as the methods of inhibition of cracking in general. For each of these stages, certain conditions are necessary. For the flow of the first stage, a source of atomic hydrogen is needed. Such source on underground pipelines is ground moisture (water) in the presence of electrochemical potential. This source only operates in places of insulation failure. Another necessary condition at the first stage is the presence of tensile mechanical stresses above a certain critical level - the stress corrosion limit. The proposed physical model has been experimentally confirmed by studying the patterns of introduction of hydrogen into the wall of the pipeline. On the basis of this physical model, it was concluded that on the main oil pipelines it is possible to develop stress corrosion cracking in local zones, where a concentration of stresses is created, and insulation in these zones either is absent or worn out.

The influence of the defects in ZnO films on the electrical and photovoltaic properties of perovskite solar cells was investigated in the work. According to the results of the research it was established that the defects in ZnO films affects the concentration of defects of perovskite films synthesized on the ZnO surface. However, the difference in the defect concentration in perovskite films is about 30%, while the concentration of defects in ZnO differs by 1000 times. A less significant influence is the concentration of ZnO defects on the electrical and photovoltaic properties of perovskite solar cells. The magnitude of the short-circuit photocurrent and the open voltage of the cells are affected by the concentration of perovskite defects and the quality of the perovskite-ZnO interface.

Small dimensional transition metal carbides (MXenes) are promising materials for the development of photocatalysts and are highly efficient cocatalysts for industrial TiO_2 (P25). Thus, in the Ti_3C_2@TiО_2 nanocomposite obtained by layering Ti_3C_2 nanoplates, the ability to separate charge carriers increases due to the high electrical conductivity of TiC_{1-х}. The task of forming the TiC_{1-х}@TiО_{2-х} nanocomposite by direct synthesis with n-TiO_2 is promising, which allows to increase the quality of contact between the shell and the nanocomposite core and to reduce the number of intermediate stages of synthesis. In addition, highly dispersed TiC has high values of hardness, melting point, modulus of elasticity and shear and has the prospect of use in materials science in plasma spraying coatings. In work ТіС was synthesized on the surface of TiO_2 - the shell of the modified micropowder TiH_2/TiO_2/С during reductive annealing in vacuum using TiH_2 as a source of atomic hydrogen. After a series of annealing at 535 ºС - 600 ºС, the Ti2p- C1s- and O1s- spectra of surface atoms were obtained. The main stages of TiC synthesis in the TiO_2/С conversion reaction were established by the XPS method. The use of TiH_2 as a source of atomic hydrogen in nanosystems of the «core/shell» type is proposed for local synthesis on the surface of nanoobjects in a vacuum or inert atmosphere.

Spherical molybdenum nano-powders were in-situ ultrafast synthesized from ammonium paramolybdate (APM) raw materials in a one-step reduction method by radio frequency (RF) hydrogen plasma. Due to the extreme conditions of the RF plasma torch such as its high temperature and large temperature gradient, the injected raw APM powder was quickly gasified and then reduced into nano-sized metal molybdenum (Mo) powder. The influences of APM powder delivery rate and H2 concentration on the properties of the obtained powders were investigated. Field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), nanolaser particle analyzer, and specific surface area method were used to characterize the morphology, phase, and particle size distribution of the powders. The results showed that the nano-sized Mo powder obtained by hydrogen plasma treatment had a quasi-spherical morphology and an average particle size of about 30 nm. The particle size could be successfully adjusted by varying H2 concentrations. In addition, spherical nano-sized MoO3 powder could be obtained when no H2 was added into the RF plasma.

In this study, we discuss Si-SiGe etch characteristics as well as SiGe surface composition modification. It is required to etch Si and SiGe simultaneously for Si/SiGe dual channel Fin-FETs. Therefore, etch control of these two materials is desired. However, not only halogen chemistries but also physical sputtering etch SiGe selective to Si. We found that Si can be etched faster than SiGe by hydrogen plasma. Our analysis presents that hydrogen bonds selectively with Si rather than Ge, which leads to Si selective removal. As for SiGe surface modification, realizing Si-rich surface in SiGe is known to improve SiGe/high-k interface quality in advanced CMOS. It is also presented that the low-temperature hydrogen plasma induces Si-surface segregation (i.e., Si-rich surface) in SiGe, which is confined near the top-surface region. We proposed this may be caused by ion-energy-driven surface reaction. Our study also shows that Ge/Si ratio increases with plasma exposure time, which has correlation with surface roughness. Using the hydrogen plasma and conventional halogen plasma, we successfully demonstrate to etch Si/SiGe dual channel fins with depth and CD value control.

From the width of the 656.3-nm Balmer /spl alpha/ line emitted from inductively and capacitively coupled radio frequency (RF), microwave, and glow-discharge plasmas, it was found that inductively coupled RF helium-hydrogen and argon-hydrogen plasmas showed extraordinary broadening corresponding to an average hydrogen atom energy of 250-310 and 180-230 eV, respectively, compared to 30-40 and 50-60 eV, respectively, for the corresponding capacitively coupled plasmas. Microwave helium-hydrogen and argon-hydrogen plasmas showed significant broadening corresponding to an average hydrogen atom energy of 180-210 and 110-130 eV, respectively. The corresponding results from the glow-discharge plasmas were 33-38 and 30-35 eV, respectively, compared to /spl ap/ 4 eV for plasmas of pure hydrogen, neon-hydrogen, and xenon-hydrogen maintained in any of the sources. Similarly, the average electron temperatures T/sub e/ for helium-hydrogen and argon-hydrogen inductively coupled RF and microwave plasmas were high (43 200 /spl plusmn/ 5% K, 18 600 /spl plusmn/ 5% K, 30 500 /spl plusmn/ 5% K, and 13 700 /spl plusmn/ 5% K, respectively); compared to 9300 /spl plusmn/ 5% K, 7300 /spl plusmn/ 5% K, 8000 /spl plusmn/ 5% K, and 6700 /spl plusmn/ 5% K for the corresponding plasmas of xenon-hydrogen and hydrogen alone, respectively. Stark broadening or acceleration of charged species due to high electric fields cannot explain the inductively coupled RF and microwave results since the electron density was low and no high field was present. Rather, a resonant energy transfer mechanism is proposed.

In this study, gallium and hydrogen co-doped ZnO (HGZO) thin films were investigated. The films were deposited by sputtering from Ga-doped ZnO (GZO) ceramic target in hydrogen and argon plasma. The as-deposited HGZO films possess enhanced electron mobility of 48.6 cm2/Vs as compared to that of 39.4 cm2/Vs of GZO films, sputtered from the same target. Because of insignificant variation in crystallinity, this improvement is attributed to roles of hydrogen in crystalline lattice structure of the films. X-ray photoelectron spectroscopy (XPS) is employed as an essential technique for quantitative analyses and chemical binding states of films constituent elements. The roles of hydrogen are clarified through the binding states of Zn 2p, O 1s and Ga 3d. Obtained results suggest that the films are deposited more effectively in hydrogen plasma. Some point defects such as oxygen vacancies (VO), dangling bonds can be passivated in form of H+VOHO and O–H bonds. As a result, the reduction of scattering centers is indicated as a reason for the mobility improvement of the HGZO films.

Promising SnOx electron transport layer for polymer solar cells

Deep center passivation in 3C-SiC by hydrogen plasma with a grid for damage suppression

Improved NO2 gas-sensing performance of PPy by hydrogen plasma treatment: Experimental study and DFT verification