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Energetic Ions during Plasma-Enhanced Atomic Layer Deposition and their Role in Tailoring Material Properties
摘要： Plasma-enhanced atomic layer deposition (PEALD) has obtained a prominent position in the synthesis of nanoscale films with precise growth control. Apart from the well-established contribution of highly reactive neutral radicals towards film growth in PEALD, the ions generated during plasma exposure can also play a significant role. In this work, we report on the measurements of ion energy and flux characteristics on grounded and biased substrates during plasma exposure to typically used for PEALD (O2, H2, N2) were measured in a commercial 200-mm remote inductively coupled plasma ALD system equipped with RF substrate biasing. IFEDFs were obtained using a gridded retarding field energy analyzer and the effect of varying ICP power, pressure and bias conditions on the ion energy and flux characteristics of the three reactive plasmas were investigated. The properties of three material examples – TiOx, HfNx and SiNx – deposited using these plasmas were investigated on the basis of the energy and flux parameters derived from IFEDFs. Material properties were analyzed in terms of the total ion energy dose delivered to a growing film in every ALD cycle, which is a product of the mean ion energy, total ion flux and plasma exposure time. The properties responded differently to the ion energy dose depending on whether it was controlled with RF substrate biasing where ion energy was enhanced, or without any biasing where plasma exposure time was increased. This indicated that material properties were influenced by whether or not ion energies exceeded energy barriers related to physical atom displacement or activation of ion-induced chemical reactions during PEALD. Furthermore, once ion energies were enhanced beyond these threshold barriers with RF substrate biasing, material properties became a function of both the enhanced ion energy and the duration for which the ion energy was enhanced during plasma exposure. These results have led to a better insight into the relation between energetic ions and the ensuing material properties, e.g., by providing energy maps of material properties in terms of the ion energy dose during PEALD. It serves to demonstrate how the measurement and control of ion energy and flux characteristics during PEALD can provide a platform for synthesizing nanoscale films with the desired material properties.
关键词： ion energy dose,ion energy flux,ion bombardment,atomic layer deposition,RFEA,thin film,substrate biasing,ion flux,ion energy control,retarding field energy analyzer,plasma ALD
更新于2025-09-23 15:21:21
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[IEEE 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Zlatibor, Serbia (2018.5.16-2018.5.20)] 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Solid-Liquid Interdiffusion Bonding Based on Au-Sn Intermetallic for High Temperature Applications
摘要： This paper covers one of the aspects of solid-liquid interdiffusion (SLID) bonding of semiconductor structures to substrate for high temperature operation. Investigations were focused on Au/Sn intermetallic compounds formed at the interface between Au metallization on the chip and Sn metallization on the DBC (Direct Bonded Copper) substrate. Two version of SLID were applied: one stage process at 350?°C and two stage process short time at 280?°C + long time at 180?°C. Second process is divided into two steps: short high temperature (280?°C) step for melting Sn and initial intermetallic compound formation and long low temperature (180?°C) step for solid state diffusion process. Design of experiments technique was used for process optimization. The best process parameters were obtained and they were applied for monocrystalline GaN chips assembly to DBC substrates. In the long-term stability tests at 300?°C it was proven that both versions of investigated SLID technique can be applied for monocrystalline GaN chips assembly. Critical condition for this assembly operation is high enough pressure applied on the chip to initiate diffusion process.
关键词： High Temperature Applications,GaN chips,Au-Sn Intermetallic,DBC substrate,Solid-Liquid Interdiffusion Bonding
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Depth profile of ZnAl<inf>2</inf> O<inf>4</inf> layer on sapphire substrate by cathodoluminescence
摘要： ZnAl2O4 for ultraviolet emitting phosphor prepared by deposition of ZnO on c-sapphire substrate and thermal diffusion process. The deflections of Zn and Al atoms in the films were confirmed by cathodo-luminescence properties. The CL intensity of ZnAl2O4 was not saturated from the film annealed for 100 hours, however, the saturation of UV emission was observed under anode voltage of 8 kV in the film annealed for 200 hours. It is thought that the thickness of ZnAl2O4 film became thinner by longer annealing at high temperature because of Zn re-evaporation. From cross-sectional FE-SEM observation, it was confirmed that the correct thickness and atomic distributions in the film. Since the ZnAl2O4 film thickness of the sample annealed for 100 hours was about 1 μm by FE-SEM, it was suitable the penetration depth of the electron into ZnAl2O4 layer
关键词： Sapphire substrate,Thermal distribution,ZnAl2O4,Ultra-Violet emission
更新于2025-09-23 15:21:21
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[NanoScience and Technology] Silicene (Prediction, Synthesis, Application) || Si Nanoribbons: From 1D to 3D Nanostructures
摘要： In this chapter we give an overview on the theoretical and experimental investigations of one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) Si nanoribbons (SiNRs) formed on the anisotropic Ag(110) substrate surface. We start by introducing briefly free-standing silicene, a silicon layer with Si atoms arranged in honeycomb lattice, with hexagonal Si-rings as structural units. These hexagonal Si units are subsequently discussed as possible candidates to explain the atomic arrangement of the experimentally synthesized Si nanoribbons on Ag(110). This interpretation is supported by properties such as the presence of the 1D projection of the π and π* bands, forming the so-called “Dirac cones” at the K points of the Brillouin zone, the sp2-like nature of the Si valence orbitals, and the strong resistance against oxidation. Besides these results, the atomic structure as well as the origin of the electronic properties of these Si nanoribbons are still controversially debated in the literature. We address this discussion in the last part of the chapter before summarizing it.
关键词： Si nanoribbons,oxidation resistance,silicene,Ag(110) substrate,Dirac cones,sp2 hybridization
更新于2025-09-23 15:21:21
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Broadside Scanning Asymmetric SIW LWA with Consistent Gain and Reduced Side Lobe
摘要： In this paper, a backwards-to-forward continuous beam scanning leaky wave antenna (LWA) is presented in substrate integrated waveguide (SIW) technology. The antenna radiates from a continuous longitudinal slot etched on its broad wall. The slot is excited by using periodic H-plane steps. An impedance matched unit cell structure is used to suppress the open stop-band in the broadside direction. Bloch wave analysis is used to obtain the propagation characteristics of the antenna. However, due to radiation being obtained only from the shunt type radiating element viz., the longitudinal slot, a gain dip is observed in the broadside direction. Transversal asymmetry is then introduced in the structure to eliminate the gain dip and obtain consistent gain. A prototype of the antenna is fabricated and measured. Continuous beam scanning is achieved from –29o to +30o about the broadside direction with a gain variation of less than 2 dB over 8.0–12.4 GHz. A measured peak gain of 16.1 dBi is obtained. Key structural design parameters of the antenna are identified for controlling the leakage rate. Next, Taylor tapered aperture illumination is used to obtain low sidelobe level (SLL). The Taylor tapered antenna is also fabricated with the measured SLL below -21 dB.
关键词： substrate integrated waveguide (SIW),broadside radiation,Taylor distribution,Leaky-wave antenna (LWA)
更新于2025-09-23 15:21:21
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Effect of substrate bias and substrate/plasma generator distance on properties of a-C:H:SiOx films synthesized by PACVD
摘要： In this paper the a-C:H:SiOx films were synthesized on silicon (100) and glass substrates by plasma-assisted chemical vapor deposition combined with pulsed bipolar substrate bias from mixtures of argon and polyphenylmethylsiloxane vapor. The process of a-C:H:SiOx films formation was investigated by controlling processing conditions such as amplitude of negative pulse of substrate bias and the distance between the substrate and plasma generator. Physico-mechanical characteristics of a-C:H:SiOx films were studied by the nanoindentation technique, atomic force microscopy, Fourier transform infrared and Raman spectroscopy. The contact angle and surface free energy were determined by the sessile drop method using couple liquids (water and glycerin). It was found that the films’ properties are interrelated with the density of the ion current on the substrate, which was measured using a guarded planar probe. The obtained results show that film prepared at the smaller substrate/plasma generator distance and optimal substrate biasing has a higher content of sp3 bonded carbon and, accordingly, has higher hardness, Young's modulus and resistance to plastic deformation. At the same time the a-C:H:SiOx films show large hydrophobicity with a contact angle for water of about 91° and small total surface free energy of about 17.9 mN/m.
关键词： a-C:H:SiOx films,PACVD,Raman Spectroscopy,Substrate bias,Fourier Transform Infrared Spectroscopy,Wettability
更新于2025-09-23 15:21:21
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Influence of 4H-SiC substrate miscut on the epitaxy and microstructure of AlGaN/GaN heterostructures
摘要： AlGaN/GaN heterostructures were grown on “on-axis” and 2° off (0001) 4H-SiC substrates by metalorganic vapor phase epitaxy (MOVPE). Structural characterization was performed by transmission electron microscopy. The dislocation density, being greater in the on-axis case, is gradually reduced in the GaN layer and is forming dislocation loops in the lower region. Steps aligned along [11?00] in the off-axis case give rise to simultaneous defect formation. In the on-axis case, an almost zero density of steps is observed, with the main origin of defects probably being the orientation mismatch at the grain boundaries between the small not fully coalesced AlN grains. V-shaped formations are observed in the AlN nucleation layer, but are more frequent in the off-axis case, probably enhanced by the presence of steps. These V-shaped formations are completely overgrown by the GaN layer, during the subsequent deposition, presenting AlGaN areas in the walls of the defect, indicating an inter-diffusion between the layers. Finally, at the AlGaN/GaN heterostructure surface in the on-axis case, V-shapes are observed, with the AlN spacer and AlGaN (21% Al) thickness on relaxed GaN exceeding the critical thickness for relaxation. On the other hand, no relaxation in the form of V-shape creation is observed in the off-axis case, probably due to the smaller AlGaN thickness (less than 21% Al). The AlN spacer layer, grown in between the heterostructure, presents a uniform thickness and clear interfaces.
关键词： TEM,HEMT,SiC substrate,Heterostructure,AlGaN/GaN,HRTEM
更新于2025-09-23 15:21:21
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Thin film technology for solar steam generation: A new dawn
摘要： The sun is considered as the most promising abundant renewable energy source that can be exploited to solve many of human beings’ challenges such as energy and water scarcity. Solar energy can be utilized in steam and vapor generation processes which has a great importance in many engineering applications such as water desalination, domestic water heating, and power generation. However, dilute solar flux (～1000 W/m2) cannot supply the absorber with enough power required to overcome water latent heat of vaporization to evaporate water. Optical concentrators such as parabolic trough collector, parabolic dish reflector, and circular Fresnel lens can be used to concentrate the solar radiation to achieve the required power however they suffer from complexity and high cost. Moreover, the efficiency of the conventional solar desalination devices such as solar stills decreases dramatically with increasing bulk water quantity, due to the heat loss to bulk water. Therefore, the need to solar steam generation (SG) devices, that localize heating on a thin layer of water rather than the water bulk, arises. Thin film technology has shown promising progress in SG in which solar energy is utilized to wastewater desalination. The past five years have seen a significant surge in the development of thin film based SG devices. In this review, recently developed thin film-based SG devices are scrutinized with respect to their physical mechanisms, fabrication methods, structure, advantages, and disadvantages. Different types of thin-film materials, including: metal-based nanoparticles, metal oxides, carbon-based materials, polymers, etc.; as well as different substrates materials, including: wood, paper, cotton fabric, carbon fabric, polystyrene foam, and gauze, have been discussed. Moreover, different preparation and synthetization methods of the steam generation devices have been discussed. Suggestions for future research directions are also presented.
关键词： Substrate materials,Heat localization,Solar energy,Steam generation,Deposition techniques,Thin film technology
更新于2025-09-23 15:21:21
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Horizontal GaN nanowires grown on Si (111) substrate: the effect of catalyst migration and coalescence
摘要： Here, we demonstrate the growth of horizontal GaN NWs on silicon (111) by a surface-directed vapour–liquid–solid (SVLS) growth. The influence of the Au/Ni catalysts migration and coalescence on the growth of the NWs has been systematically studied. A 2-D root-like branched NWs were gown spontaneously through catalyst migration. Furthermore, a novel phenomenon that a catalyst particle is embedded in a horizontal NW was observed and attributed the destruction of growth steady state due to the catalysts coalescence. The transmission electron microscopy (TEM) and photoluminescence (PL), cathodoluminescence (CL) measurement demonstrated that the horizontal NWs exhibit single crystalline structures and good optical properties. Our work sheds light on the horizontal NWs growth and should facilitate the development of highly integrated III?V nanodevices on silicon.
关键词： GaN nanowires,silicon substrate,coalescence,catalyst migration,SVLS growth
更新于2025-09-23 15:21:21
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Design of duala??functional substratea??integrated waveguide cavity with integration of filter and antennas
摘要： A dual-functional substrate-integrated waveguide (SIW) cavity which integrates a filter and two antennas is proposed in this article. Three slots are etched to divide a single cavity into four quarter-mode subcavities. Two equal subcavities are utilized to design a second-order filter. Mixed coupling is induced by this slot-etched structure, where a controllable transmission zero can be generated in the lower or upper stopband. Two unequal subcavities are utilized to design two integrated antennas. By adjusting their areas, the frequency ratio of these two antennas achieves a wide range of 0.55-1.81. In addition, the overall port isolation of higher than 21.0 dB is obtained by optimizing slot length. The proposed design has been validated by experimental results of a fabricated prototype. With advantages of low profile, light weight, suitable isolation, and flexible design, it has potential applications for modern wireless communication.
关键词： dual function,filters and antennas,etched slots,substrate-integrated waveguide (SIW) cavity,quarter modes
更新于2025-09-23 15:21:01