Nanoscale metal-silicide films prepared by surfactant sputtering and analyzed by RBS

Surfactant sputtering has been applied to modify the surface structure of Si substrates and to produce ultrathin metal-silicide films with nickel and platinum surfactants, utilizing the steady state coverage of a Si-substrate surface with surfactant atoms simultaneously during sputter erosion by combined ion irradiation and surfactant atom deposition. Si (1 0 0) substrates were eroded using 5 keV Xe-ions and 10–30 keV Ar ions at incident angles of 65° and 70° with fluences of up to 2 × 10¹⁸/cm² under continuous sputter deposition of platinum and nickel from targets irradiated simultaneously by the same ion beam. These surfactant atoms form metal-silicides in the surface near region and strongly modify the substrate sputter yield and the surface nanostructure. Atomic force microscopy and scanning electron microscopy were carried out to observe a transition of surface topography from ripple to relief patterns, granular patterns or smooth surfaces. The Si and metal sputter yield as function of the steady state metal coverage were determined by combination of Rutherford-backscattering spectroscopy (RBS) and profilometry. The composition and the depth distributions of metal-silicide films were analyzed via high-resolution RBS and transmission electron microscopy. We show that RBS results in comparison with SRIM and TRIDYN sputter yield simulations allows us to identify the silicide surface structure on the nanometer scale.     

Fundamentals of surfactant sputtering

We introduce a new sputter technique, utilizing the steady-state coverage of a substrate surface with up to 10¹⁶ cm⁻² of foreign atoms simultaneously during sputter erosion by combined ion irradiation and atom deposition. These atoms strongly modify the substrate sputter yield on atomic to macroscopic length scales and therefore act as surfactant atoms (a blend of “surface active agent”). Depending on the surfactant-substrate combination, the novel technique allows enhanced surface smoothing, generation of novel surface patterns, shaping of surfaces and formation of ultra-thin films. Sputter yield attenuation is demonstrated for sputtering of Si and Fe substrates and different surfactant species using 5 keV Xe ions at different incidence angles and fluences up to 10¹⁷ cm⁻². Analytical approaches and Monte Carlo simulations are used to predict the sputtering yield attenuation as function of surfactant coverage. For sputtering of Si with Au surfactants we observe high sputter yields despite a steady-state surfactant coverage, which can be explained by strong ion-induced interdiffusion of substrate and surfactant atoms and the formation of a buried Au_xSi surfactant layer in dynamic equilibrium.     

Characteristics of TiVCrAlZr multi-element nitride films prepared by reactive sputtering

Nitride films of multi-element TiVCrAlZr alloy were prepared on silicon substrates by reactive radio-frequency magnetron sputtering under different nitrogen/argon flow ratios ranging from 0% to 66.7%. The alloy film deposited in pure argon exhibited an amorphous structure and a very smooth surface, while a face-center-cubic solid-solution structure with strong (2 2 0), (1 1 1) to (2 0 0) orientation and different fracture feature and surface morphologies was observed in those films which were prepared under various nitrogen flow ratios. With increasing nitrogen flow ratio, the hardness and elastic modulus of the films increased and reached maximum values of 11 and 151 GPa at 50%.     

Ion implantation studies on VOx films prepared by pulsed dc reactive sputtering

Vanadium oxide (VO_x) thin films find extensive use in room-temperature bolometers for IR imaging. It is desirable to control and modify the electronic properties of this temperature-sensitive material with treatments such as ion implantation and thermal annealing. In this work, we report on the modification of structural and electrical properties of VO_x thin films of varying compositions, deposited by pulsed dc reactive sputtering using a vanadium target under different oxygen flow rates. The as-deposited resistivities of the films ranged from 0.1 Ω cm to 100 Ω cm and the temperature coefficient of resistance (TCR) values varied from ?1.1% to ?2.7%. VO_x films used in microbolometers need to have a high TCR (>2%) and low resistivity values (1–10 Ω cm) in order to maximize sensitivity in conjunction with the read-out integrated circuit (ROIC). However, one usually finds a high TCR associated with high resistivity. Hence ion implantation followed by annealing was performed with the goal of improving the trade-off between TCR and resistivity. Two species – hydrogen (active) and helium (inert) – were chosen for implantation. Hydrogen is strongly electroactive and is well known for passivating defect states in a wide variety of electronic materials. As inert species, helium was chosen mainly to study the effects of bombardment on the film. The implanted films were annealed in an inert atmosphere to allow defect control and redistribution of atoms, and then characterized by current–voltage measurements over a wide temperature range. An order of magnitude change in resistance, and significant variations in TCR were observed. Further characterization has been done by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to correlate these resistivity changes with the structure of the films.     

Modelling the erosion of beryllium carbide surfaces

Redeposition of beryllium eroded from main chamber plasma facing components of ITER onto the divertor material carbon creates a mixed material, beryllium carbide Be₂C, whose interaction with the plasma is not well known. In this study, we have investigated the erosion of Be₂C by deuterium using molecular dynamics simulations and ERO impurity modelling. We found that beryllium sputters preferentially over carbon and identified the sputtering mechanism in the ion energy range 10-100 eV to be both physical and swift chemical sputtering. In addition to single atoms, different types of small molecules/clusters were sputtered, the most frequently occurring molecules being BeD, Be₂D, and CD. The sputtering threshold was found to lie between 10 and 15 eV. The MD sputtering yields were used in plasma impurity simulations, serving as a replacement for input data obtained with TRIM. This changes the accumulation rate of impurity Be in the divertor region compared to previous estimates.     

Chemical sputtering of deuterated carbon surfaces at various surface temperatures

The chemical sputtering of deuterated amorphous carbon (a-C:D) surfaces irradiated by 1-50 eV deuterium atoms at surface temperatures between 300 and 1000 K was studied using classical molecular dynamics. A quasi-stationary state was reached by cumulative bombardment for each energy and temperature. Results were compared with available experimental data and previous modeling results and the applicability of molecular dynamics for thermally generated processes was discussed. An attempt is made to correct the absence of the thermally stimulated desorption/degassing of hydrogen from the MD simulations, which evolve at the longer time scales.     

Structure and tribological properties of Ti-containing amorphous carbon coatings prepared by cathode arc-enhanced middle-frequency magnetron sputtering

Ti-containing amorphous carbon （Ti-aC） coatings were deposited on cemented carbide and Si substratcs by cathode-arc-enhanced closed field middle-frequency unbalanced magnetron sputtering. The coatings were studied by using atomic force microscopy, Raman scattering, nanoindentation, and pin-on-disk testing. The measurements showed that the hardness of the coatings increased from 12 GPa at a Ti content of 1 at.% to 27 GPa at 31 at.%. The coatings exhibited different friction behaviors when facing different mating materials and changed with increasing Ti content, The coating with 4 at.% Ti exhibited excellent tribological performance with a low friction coefficient of 0.07 when facing the cemented carbide.     

Growth and structural properties of silicon on Ag films prepared by 40.68 MHz very-high-frequency magnetron sputtering

The growth of silicon on Ag films via 40.68 MHz very-high-frequency (VHF) magnetron sputtering was investigated.The energy distribution and flux density of the ions on the substrate were also measured.The results showed that 40.68 MHz magnetron sputtering can produce ions with higher energy and lower flux density.The impact of these ions onto the grown surface promotes the growth of silicon,which is related to the crystalline nature and rnicrostructure of the underlayer of the Ag films,and there is large particle growth of silicon on Ag films with a preferred orientation of (111),and two-dimensional growth of silicon on Ag films with a better face-centered cubic structure.     

偏压对ECR-微波等离子增强沉积ZrN薄膜的结构及性能的影响

利用ECR-微波等离子溅射沉积技术加不同偏压在45#钢基体上制备了ZrN薄膜。利用X射线衍射仪(XRD)、透射电子显微镜(TEM)对薄膜的微观组织结构进行了分析。结果表明,无偏压时薄膜为非晶膜,随着偏压的升高,薄膜呈ZrN晶体结构。利用扫描电镜(SEM)、原子力显微镜(AFM)测试了薄膜表面形貌。薄膜表面平整,但仍存在局部缺陷;粗糙度(RMS)在0.311—0．811nm之间变化,轮廓算术平均值(Ra)在0．239-0．629nm之间变化。同时利用电化学极化实验在0．5mol／LNaCl溶液中测试了基体及薄膜的耐蚀性能,基体自腐蚀电位Ecorr为-512．3mV,样品Ecprr在-400．3--482．6mV之间变化,45#钢基体自腐蚀电流Icorr为9．036μA,样品Icorr。在0．142—0．694μA之间变化。并讨论了偏压对薄膜的微观组织和耐蚀性能产生影响的原因。     

Growth, characterization and effect of substrate bias on ZnO prepared by reactive capillaritron ion beam sputtering deposition

ZnO thin films have been deposited on Si substrates by reactive ion beam sputtering deposition utilizing a capillaritron ion source. All the as-deposited ZnO films exhibit a preferred (0 0 2) growth direction while the grain size increases as oxygen partial flow rate increases. An optimum photoluminescence result was achieved using oxygen partial flow rate of ∼40% that the ratio of integrated deep level emission to that of integrated near-band-edge emission is less than 1.5. The atomic percentage ratio of Zn:O remains at 55/45, regardless of oxygen partial flow rates. With the applied substrate bias, the atomic percentage ratio of Zn/O changes to 40/60, indicating that stoichiometric ZnO may be achieved by selecting appropriate substrate bias. With the substrate bias applied, increased amount of oxygen atoms were found located in oxygen deficient matrixes, likely due to the bombardment of secondary ions.     

Molecular dynamics simulations of low-energy argon ion sputtering of copper clusters on polyethylene surfaces

The normal bombardment of the targets consisted of single 13-, 27- or 39-atom copper cluster on a surface of polyethylene by Ar ions with energies of 100, 200 and 400 eV is examined using molecular dynamics simulation incorporating long-range many-body covalent bonding potential for hydrocarbons and a potential based on a embedded atom model for copper. Sputtering yield and its dependence on the energy of bombarding ion and size of the pre-deposited copper cluster are discussed.     

Characterization and dielectric properties of GeOx thin films prepared by radio frequency (RF) reactive sputtering

Dielectric properties of germanium oxide have not been investigated in detail. But, it has been investigated from an optical viewpoint as light waveguide materials. Its electrical properties have rarely been studied for electronic device applications.We have examined the previous investigations on Ge-O films deposited by radio frequency (RF) reactive sputtering. The dissipation factor tan δ, the capacitance per area, the breakdown field of GeO_x films were studied as well as its composition by RBS analysis. Aiming at obtaining the higher value of the dielectric constant or capacitance per area, we have attempted to fabricate Ge-Pb-O films by the same deposition method. An optimization of the dielectric properties of these materials has been done, using the best conditions of sputtering for each oxide, the alternated pile layers as dielectric multilayer capacitors and thermal treatments.These dielectric properties have been improved by thermal treatments, and the dielectric multilayer made with alternated GeO₂ and Ge-Pb-O films capacitors has a breakdown field superior to that of each simple layer.     

中频磁控溅射制备AlN薄膜

设计了一套阳极层离子源辅助中频磁控溅射装置,并在Si(111)衬底上沉积AlN薄膜。用X射线衍射、原子力显微镜和扫描电镜分析了AlN薄膜的结构、形貌和成分。在优化的实验条件下制备的AlN薄膜具有较强的(002)衍射峰,其半高宽为612–648弧秒。气体流量、衬底偏压、离子源等对薄膜结构有明显影响。     

中频磁控溅射制备AIN薄膜

设计了-套阳极层离子源辅助中频磁控溅射装置,并在Si(111)衬底上沉积AIN薄膜.用X射线衍射、原子力显微镜和扫描电镜分析了AIN薄膜的结构、形貌和成分.在优化的实验条件下制备的AIN薄膜具有较强的(002)衍射峰,其半高宽为612-648弧秒.气体流量、衬底偏压、离子源等对薄膜结构有明显影响.     

CrN films deposited by ion source-assisted magnetron sputtering

CrN coatings were deposited on Si(100) and piston rings by ion source assisted 40 kHz magnetron sputtering.Structure and composition of the coatings were characterized by X-ray diffraction,atomic force microscopy,scanning electron microscopy and transmission electron microscopy.Mechanical and tribological properties were assessed by microhardness and pin-on-disc testing.The ion source-assisted system has a deposition rate of 3.88 μm/h,against 2.2 μm/h without ion-source assistance.The CrN coatings prepared with ion source assistance exhibited an increase in microhardness(up to 16.3 GPa) and decrease in friction coefficient(down to 0.48) at the optimized cathode source-to-substrate distance.Under optimized conditions,CrN coatings were deposited on piston rings,with a thickness of 25 μm and hardness of 17.85 GPa.     

Mechanisms and theory of physical sputtering by particle impact

This article summarizes theoretical work on sputtering during the past decade, with the emphasis on elemental sputtering in the linear cascade and spike regimes as well as alloy sputtering. The sputtering of molecules and clusters, and electronic sputtering of insulators and biomolecular materials are discussed more briefly, and topics like charge and excitation states of sputtered particles as well as surface topography are left out, in view of contemporary summary papers in this issue and elsewhere. The paper is nontutorial and assumes some general knowledge of the field on the part of the reader, based e.g. on ref. [1] or ref. [2]. The discussion emphasizes principles and methods as well as open problems rather than quantitative results. A few general recommendations for efficient utilization of computer simulation conclude the paper.     

Coefficient of surface sputtering of solids by light ions

Translated from Atomnaya Énergiya, Vol. 69, No. 2, pp. 104–106, August, 1990.     

直流磁控溅射法制备含氦铝膜

采用氦氩混合气氛下直流磁控溅射沉积方法制备含有氦原子的金属铝膜。经碳原子弹性前冲散射分析（C-ERDA），薄膜中氦原子浓度可达约7％，且分布均匀。实验研究了薄膜中的氦含量与溅射真空室气氛中氦的相对含量、基底偏压及沉积温度间的关系。薄膜的X射线衍射分析结果显示：膜中的氦含量变化并未引起明显的峰位移，只是随氦含量增加谱峰宽化。热释放实验证实，氦在薄膜中稳定存在，约500℃以上时方出现氦的释放。