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Structural and electrical properties of a Ge(111) layer directly grown on a Si(111) substrate are studied. Via optimized two-step growth manner, we form a high-quality relaxed Ge layer, where strain-relieving dislocations are confined close to a Ge/Si interface. Consequently, a density of holes, which unintentionally come from crystal defects, is highly suppressed below 4 × 10 16 cm − 3 , which leads to significantly high hole Hall mobility exceeding 1500 cm 2 /Vs at room temperature. By layer transfer of the grown Ge layer, we also fabricate a Ge(111)-on-Insulator, which is a promising template for high-performance Ge-based electronic and photonic devices.

GeSn with a high substitutional Sn concentration (> 7%) is an attractive direct band gap material for high-efficiency photodevices that can be merged with large-scale integrated circuits (LSIs). To achieve GeSn with high Sn concentration, low-temperature solid-phase epitaxy using amorphous-GeSn (a-GeSn) (Sn concentration: 10%–36%)/crystal-Ge (c-Ge) stacked structures was investigated. Solid-phase growth of GeSn was enhanced as Sn concentration was increased, which enabled epitaxial growth at very low temperature (150–200 °C). Interestingly, concentrations of substitutional Sn increased with decreasing growth temperature. As a result, epitaxial growth of GeSn with substitutional Sn concentrations of ~ 8% was achieved by decreasing the growth temperature to 150 °C using a-GeSn (Sn concentration: 36%)/c-Ge stacked structures. This technique is expected to be useful to realize multi-function LSIs, where high-efficiency photodevices are integrated with transistors.

We demonstrate the (111)-oriented Ge-on-Insulator (GOI) formed by Ge epitaxial growth on a Si(111) and the layer transfer technique. The two-step growth manner, involving low-temperature growth of a thin Ge layer and subsequent high-temperature growth of a thick Ge layer, enables us to obtain high-quality tensile-strained epitaxial Ge(111) on Si(111). It is found that the strain amount straongly depends on the growth temperatures and we find an optimal growth temperature. We also developed a chemical mechanical polishing (CMP) method modified for Ge, offering the ultra-smooth Ge(111) surface. The polished epitaxial Ge is bonded on a SiO2/Si, followed by the selective etching of Si and the final CMP of Ge. As a result, we achieve the high-quality 200-nm-thick tensile-strained Ge(111)-OI with an ultra-smooth surface, on which, furthermore, we demonstrate the growth of an epitaxial metallic silicide for the metal source/drain in spintronic devices as well as advanced Ge channel devices.

We have explored an effect of the interface resistance of Fe3Si/n+-Ge Schottky-tunnel contacts on spin accumulation created electrically in n-Ge. Using the Schottky-tunnel contacts with a relatively high interface resistance, we can clearly detect spin-accumulation signals in n-Ge even at room temperature, meaning that the use of highly resistive Schottky tunnel contacts is effective to electrically create large spin accumulation. Since such highly resistive source and drain electrodes are not available for next-generation Ge-based spintronic applications with ultra-low power consumption, the development of highly spin-polarized spin injectors such as half-metallic materials is essential from now on.

For high-performance spin injectors in silicon (Si)-based spintronic applications, we have explored the growth technique of quaternary Co-based Heusler-compound Co2FeSi0.5Al0.5 on Si(111) by using low-temperature molecular beam epitaxy (LTMBE). In our previous study, Al co-deposition induced an interfacial reaction between Co2FeSi1 − xAlx and Si. Here, we dramatically improve the Co2FeSi0.5Al0.5/Si heterostructures by introducing a nonstoichiometric LTMBE technique. Atomically smooth Co2FeSi0.5Al0.5/Si heterointerfaces and L21-ordered Co2FeSi0.5Al0.5 films are simultaneously achieved. Even in as-grown conditions, the magnetic properties of the Co2FeSi0.5Al0.5 layers are nearly equivalent to those of the heat-treated ones reported on MgO. This study gives important knowledge to realize the optimized highly spin-polarized ferromagnet/Si heterointerfaces for next-generation Si-based spintronic devices.

The low-temperature-crystallization effects of soft X-ray irradiation on the structural properties of amorphous Si and amorphous Ge films were investigated. From the differences in crystallization between Si and Ge, it was found that the effects of soft X-ray irradiation on the crystallization strongly depended on the energy band gap and energy level. The crystallization temperatures of the amorphous Si and amorphous Ge films decreased from 953 K to 853 K and 773 K to 663 K, respectively. The decrease in crystallization temperature was also related to atoms transitioning into a quasi-nucleic phase in the films. The ratio of electron excitation and migration effects to thermal effects was controlled using the storage-ring current (photon flux density). Therefore, we believe that low-temperature crystallization can be realized by controlling atomic migration through electron excitation.

A low-temperature formation technique of Sn-doped Ge on insulator has been investigated by aluminum-induced crystallization using a-GeSn/Al stacked structures. For a-GeSn films (Sn concentration: 2%), the layer-exchange growth temperature is significantly decreased compared with a-Ge, which enables low temperature growth at 250°C. At such a low temperature, bulk nucleation of GeSn in Al layers is significantly suppressed, and (100)-oriented interface nucleation becomes dominant. On the other hand, growth rate becomes high by Sn-doping effects. As a result, formation of (100)-oriented large-grain (>10 μm) Sn-doped Ge (Sn concentration: 2%) crystals on insulating substrates becomes possible at a low temperature (250°C). This technique will be useful to realize advanced flexible electronics.

For spintronic applications compatible with silicon (Si) large scale integrated circuits, we have so far developed the growth technique of a Co-based Heusler-compound film, Co2FeSi, on Si by using low-temperature molecular beam epitaxy. In this study, we explore an addition technique of a fourth element, Al, to the Co2FeSi films in order to tune the number of the valence electrons and to realize the high-performance spintronic devices. We can demonstrate L21-ordered Co 2 F e S i 0.5 A l 0.5 films using Al co-deposition although 4-nm-thick reaction layers are formed at the interface. A possible mechanism of the epitaxial growth of quaternary Co 2 F e S i 1 − x A l x films on Si is discussed.

We comprehensively investigate Al-induced crystallization (AIC) of Si to achieve (0 0 1) and (1 1 1)-oriented Si films on quartz substrates. These phenomena are systematically explained by ‘preferential interfacial-nucleation model’ considering the nucleation sites and the phase transition of the interfacial Al oxide layers. Moreover, we demonstrate the lateral liquid phase epitaxy of Ge by using the orientation-controlled AIC-Si films as crystal seed. This technique enables high quality hetero-epitaxy of SiGe and Ge on transparent insulating substrates.

Low-temperature ( 1 − x Ge x (0 x 1 − x Ge x /Al/quartz stacked structures. It was found that the crystal growth features drastically depends on the Ge fraction. Change of the stacked structures to Al/poly-SiGe/quartz uniformly occurred by annealing for low Ge fractions ( 50%). To realize uniform crystallization for high Ge fractions, effects of interfacial Al oxide layer thickness on layer exchange were investigated. By optimizing the oxide layer thickness, the layer exchange process could be controlled, and thus, homogeneous crystallization with large grain sizes (> 20 μm) was achieved for samples with the whole Ge fractions. These findings will be a powerful tool for realizing large poly-SiGe on insulating films for high-efficiency thin-film solar cells and system-in-displays.

Giant growth (~ 400 μm length) of single crystalline Ge on insulator (GOI) with (100), (110), and (111) orientations is demonstrated by lateral liquid-phase epitaxy (L-LPE) using Si(100), (110), and (111) substrates, respectively, as the seeds. The micro-probe Raman measurements and transmission electron microscopy observations showed that the growth regions were of very high crystal quality and were defect free. In addition, lateral diffusion of Si atoms was observed only in the regions near the seeding edges (~ 100 μm). Based on these findings, the trigger for the giant growth of the high-quality GOI was discussed considering the solidification temperature gradient due to Si–Ge mixing and the thermal gradient due to the latent heat at the growth front.

The carrier concentration and mobility of intrinsic holes in poly-Ge films grown by solid-phase crystallization (SPC) were investigated. The two-step SPC method, consisting of low-temperature annealing (425 °C) to obtain large grains and subsequent high-temperature annealing (500 °C) to decrease defects, is proposed. The hole concentration remarkably decreased from 1 × 10 18 to 5 × 10 17 cm −3 with keeping a high-mobility (140 cm 2 /Vs) after post-annealing.

Effects of Fe/Si ratio and growth temperature were investigated in order to realize high quality Fe3Si/Ge structures. It was found that very small Xmin values (2-3%) were achieved in a wide temperature range of 60-200°C under the stoichiometric condition. From TEM observation, it was rvealed that the Fe3Si/Ge structures with atomically flat interfaces were realized. In addition, thermal stability of the Fe3Si/Ge structures was guaranteed up to 400°C. These results suggested that growth at a low temperature (

Influence of substrate orientation on epitaxial growth of the ferromagnetic silicide Fe 3 Si on Si was investigated using low temperature (60-300 °C) molecular beam epitaxy. Transmission electron microscopy (TEM) measurements revealed that Fe 3 Si layers were epitaxially grown on Si (110) and Si(lll), while random poly-crystal Fe 3 Si layers were formed on Si(100). From the Rutherford backscattering spectroscopy measurements, the values of the ℵ min of the Fe 3 Si layers grown at 60 °C on Si(100), Si(110), and Si(111) were evaluated to be 100%, 97%, and 41%, respectively. This dependence on the substrate orientation was explained on the basis of the atomic alignments at the Fe 3 Si/Si interfaces.

The oxidation-induced Ge condensation process of SiGe/Si on insulator structures has been investigated. The relaxation rate obtained in the SiGe layers on insulator (SGOI) abruptly decreased with decreasing SGOI thickness below 50 nm. In order to enhance the relaxation rate in the ultra-thin SGOI, the new technique combined with H+ irradiation with a medium dose (5 × 1015 cm− 2) and post-annealing (1200 °C) has been developed. It was demonstrated that the highly relaxed (70%) ultra-thin SGOI with a low defect density (8 × 106 cm− 2) has been realized by this technique.

Ni-mediated lateral crystallization of amorphous Si has been investigated under a wide range of electric fields (0–4000 V/cm). In the low field region ( 2000 V/cm), directional growth aligned to the electric field was observed. These new findings will be a powerful tool to achieve new poly-Si with highly controlled structures.

Au-induced lateral crystallization of amorphous Si 1− x Ge x ( x : 0–1) on SiO 2 at a low temperature (400 °C) has been investigated. Although the growth velocity decreased with increasing Ge fraction, growth velocity exceeding 20 μm/h was obtained for all Ge fractions. As a result, poly-Si 1− x Ge x with large areas (> 20 μm) was obtained at a low temperature (400 °C). This is a great advantage of Au-induced lateral crystallization compared with Ni. However, the concentrations in the surface regions (depth: 0–20 nm) of the lateral growth regions were high (10–30%), though those in the deeper regions (depth: 20–50 nm) were as small as 1–2%. Removing of the surface regions with the high Au concentrations and gettering of Au atoms in the deeper regions are necessary to apply the grown layers to the device fabrication.

Ni metal-induced lateral crystallization (Ni-MILC) of amorphous Si 0.6 Ge 0.4 thin films has been investigated by means of scanning electron microscopy and transmission electron microscopy. A pattern of Ni about 5 nm thick was fabricated to cover selective areas of the a-Si 0.6 Ge 0.4 film. Subsequently, the thin film was annealed at 550 °C for various lengths of time. In the area covered with Ni, Ni atoms diffuse into the SiGe film and react with Ge to produce precipitates of Ni 2 Ge, leaving amorphous Si. In the area outside of the Ni-covered one, on the other hand, crystallization occurs to form aggregates of small Si 0.6 Ge 0.4 grains without Ni incorporation. In the MILC process, the kind of Ni compound phase changes with the amount of diffusing Ni and the lateral crystallization should be induced by the formation of NiSi 2 .

Morphological changes of Co nanodots on SiO 2 layers by thermal treatment have been investigated. Co nanodots were formed by molecular beam deposition of Co on SiO 2 layers with substrate temperatures (30–600 °C) and subsequent post-annealing (500–800 °C). For samples deposited at low temperatures (30–280 °C), the diameter and the density of nanodots increased and decreased, respectively, with increasing post-annealing temperature. On the other hand, the diameter and the density of nanodots scarcely changed by post-annealing for samples deposited at high temperatures (430–600 °C). These morphological changes by the post-annealing can be explained on the basis of the stress relaxation in the deposited Co films.

The low-temperature ( 2000 V/cm). These new findings will be a powerful tool for achieving new poly-SiGe with highly controlled crystal structures.

Pulsed-XeCl excimer laser crystallization of germanium (Ge) and silicon–germanium (SiGe) alloy films formed on quartz glass substrates was investigated. The transient conductance measurements reveled that germanium films were rapidly melted and solidified because of low latent heat compared to silicon films. Formation of silicon–germanium alloy was also observed in the case of laser annealing the Ge/Si layered structure. The crystalline volume ratio was estimated almost 1.0 for Si0.4Ge0.6 films because of small disordered electronic states at grain boundaries, while it was 0.85 for Si films. D 2005 Elsevier B.V. All rights reserved.

Metal-induced lateral crystallization of amorphous Si has been investigated under a wide range of electric fields (0–4000 V/cm). In the low field region ( 2000 V/cm), directional growth aligned to the electric field was observed. This new findings will be a powerful tool to achieve new poly Si with highly controlled structures.

Au-induced low-temperature (400 °C) crystallization of amorphous-Si1−xGex (x: 0–1) thin films on SiO2 has been investigated. Although the growth velocity decreased with increasing Ge fraction, growth velocity exceeding 20 μ m/h was obtained in all Ge fractions. As a result, strain-free poly-Si1−xGex with large areas (>20 μ m) were obtained at a low temperature (400 °C). These new polycrystalline SiGe films on insulator could be used for advanced system in display and three-dimensional ULSI.

The effects of local Ge doping on the crystal nucleation in the solid-phase crystallization (SPC) of a-Si films on SiO 2 films were investigated. Three types of sample structures, (a) a-Si/a-Ge/a-Si/SiO 2 , (b) a-Si/a-Ge/SiO 2 , and (c) SiO 2 /a-Ge/a-Si/SiO 2 , were prepared and annealed at 600 °C. For the structure (a) with a thin (∼5 nm) Ge film, Ge atoms completely diffused into a-Si films, and SPC was not enhanced. On the other hand, for the structure (a) with Ge films thicker than 10 nm, Ge atoms were localized at the initial position. Such abnormal retardation of Ge diffusion was remarkable for the structures (b) and (c) even for samples with thin Ge films. For samples with Ge localization, significant enhancement of SPC of a-Si was observed. These results indicated that crystal nucleation was initiated in the localized Ge films, and then propagated into a-Si films. The local Ge doping at a-Si/SiO 2 interfaces can be employed to selectively induce the nucleation at the interfaces.

Carrier transport in ion-beam synthesized (IBS) β-FeSi2 was investigated by using Hall effect measurement at low temperatures (15–300 K). The measurement showed p-type conduction in the temperature range of 15–300 K. The Hall coefficient increased with increasing temperature up to 25 K, and then it decreased, which suggested the two carrier conduction, i.e., the impurity conduction, as well as the conduction in the valence band, play an important role in the carrier transport. Based on the two carrier model, the hole concentration and mobility for the impurity conduction at 25 K were evaluated to be 9.9×1017 cm−3 and 0.85 cm2 V−1 s−1, respectively, which suggested that the acceptors were isolated and did not form the impurity band at the impurity concentration of 9.9×1017 cm−3. Thus, the threshold concentration for the impurity band formation was more than three orders of magnitude higher than that for GaAs (2×1016 cm−3), which could be explained on the basis of the Mott criterion.

Electrical and structural properties of polycrystalline silicon germanium (poly-SiGe) films fabricated by pulsed-laser annealing were investigated. Observation of laser-induced melt-regrowth of SiGe films using transient conductance measurement revealed that the melt depth and the crystallization velocity increased as Ge concentration increased. The increase of the crystallization velocity resulted in increase of the average size of crystalline grains from 66 to 120 nm at the laser energy density of 360 mJ/cm2 with increasing Ge concentration from 0 to 60%. The crystalline volume ratio obtained by reflectivity spectra in the ultraviolet region also increased from 0.83 to 1.0. Numerical analysis revealed that the density of electrically active defects decreased from 3.5×1018 to 1.1×1018 cm−3 as Ge concentration increased from 0 to 80%. The density of defect states of Si0.8Ge0.2 films were reduced from 3.5×1018 to 1.9×1018 cm−3 by 13.56-MHz hydrogen plasma treatment at 250 °C, 30 W, and 130 Pa for 30 s. How...

Low-temperature (≤550 °C) Ni-mediated crystallization of amorphous SiGe (a-Si 1-x Ge x (0 ≤ x ≤ 1)) layers on SiO 2 films has been investigated. The morphology of crystallized SiGe strongly depended on the Ge fraction. For low Ge fractions (

Effects of local Ge-insertion in a-Si films on solid-phase crystallization (SPC) were investigated. Three types of stacked structures, i.e. (a) a-Si/a-Ge/a-Si/SiO 2 , (b) a-Si/a-Ge/SiO 2 and (c) SiO 2 /a-Ge/a-Si/SiO 2 were fabricated and annealed at 600 °C. The results for the structure (a) showed that Ge atoms diffused into the Si layers, and no-enhanced SPC was detected. On the other hand, the results for the structures (b) and (c) indicated that Ge atoms were localized in the initial position. In addition, significant enhancement of SPC of a-Si was found. These results indicated that crystal nucleation was initiated at Ge layers directly contacted to SiO 2 , and then propagated into a-Si layer. Consequently, interface nucleation driven SPC becomes possible by using the structures (b) and (c). This will be a useful tool to achieve growth of Si crystals with a preferential orientation on SiO 2 .

The metal-induced low-temperature (≤550°C) crystallization of a-Si1-xGex (0 ≤x ≤1) on SiO2 has been investigated. A Ge-fraction-dependent crystal growth was observed. In the case of a low-Ge fraction, plane growth dominated, the velocity of which was enhanced by 80% with increasing Ge fraction from 0 to 20%. This produced strain-free poly-SiGe with large grains (18 µm). On the other hand, dendrite growth became dominant in the case of intermediate Ge fractions (40–60%). By optimizing the growth conditions (x: 0.4, annealing: 450°C, 20 h), very sharp needlelike crystals (width: 0.05 µm, length: 10 µm) were obtained. These new polycrystalline SiGe films on insulator should be used for system-in-display, three-dimensional ultra large-scall integrated circuits, and novel one-dimensional wires.

We have demonstrated epitaxial growth of Ge 1-x Sn x layers on Fe 3 Si by low-temperature MBE. We believe that this technique can be applicable to the growth of Ge 1-x Sn x on various ferromagnetic metallic templates toward high-performance spin-based MOSFETs.

Modulation-doped SiGe/Si/SiGe heterostructures were grown by molecular-beam epitaxy (MBE), and n-type field-effect transistors were fabricated. Electrons transferred to the strained-Si channel increased the electron density to up to 1×10 12 cm −2 with increasing gate voltage, then excess electrons remained in the SiGe doping layer under a higher gate voltage. A device simulation explained this phenomenon well and suggested that device performance can be improved by increasing the Ge content in the SiGe layer to ∼0.5.

Distribution of delta-doped Sb atoms in a Si 1− x Ge x layer was studied by using a new method combining chemical treatment and inductively-coupled-plasma mass spectrometry, and thermal diffusion of the Sb atoms was studied by secondary-ion mass spectrometry (SIMS). The delta doping was performed as follows: First, 0.1-monolayer Sb atoms were deposited on Si 1− x Ge x surfaces and embedded by evaporating amorphous Si 1− x Ge x layers on them at room temperature in order to reduce the surface segregation phenomenon. Then the amorphous Si 1− x Ge x layers were crystallized by heating at 600°C. The initial width of the Sb-doping profile is only about 1 nm in pure Si. The width increases with increasing Ge content in the Si 1− x Ge x layers. Moreover, secondary ion mass spectrometry (SIMS) analysis shows that Ge atoms strongly enhance the thermal diffusion of Sb, and the diffusion enhancement is attributed to the decrease in activation energy of diffusion caused by the existence of Ge atoms in the Si 1− x Ge x layers.

Solid-phase crystallization (SPC) properties of Si 1− x Ge x (0≦ x ≦0.3) layers on SiO 2 have been investigated by using ellipsometric spectroscopy. Crystallinity of the SiGe layers abruptly increased in the middle of an annealing time and gradually saturated at values fairly below that of the single-crystal state. The incubation time of the nucleation significantly decreases with increasing x ; the estimated incubation time in Si 0.7 Ge 0.3 is about 1/100 of that in Si. During the incubation time, it was observed that the crystallinity of SiGe layers continuously increased with increasing annealing time. This phenomenon represents the growth of some state precursory to nucleation which could not be observed by conventional methods. Since band structure is sensitive to the number of atoms in ordered positions, atomic rearrangements before the nucleation may be observed by present work. The crystallization time, defined as the time to complete SPC after nucleation, also showed a decrease with increasing x . The decrease in Si–Si bond energy caused by the introduction of Ge reduces the activation energy for lattice rearrangement and thus enhances the SPC of Si.

The potential energies of a Ge atom in the three top layers of Si(1 0 0) surfaces were evaluated by accurate density functional calculations of the model clusters and compared with the previously reported potential energies for B, Ga, and Sb. The order of resistance to surface segregation of all of these elements can be understood primarily by considering the bond energies between the element and Si atoms as the driving force for segregation. Though the potential energy curve for Ge has a minima in the first layer, it is so shallow that Ge shows a moderate tendency towards surface segregation.

Surface segregation of antimony atoms during Si 1− x Ge x molecular beam epitaxy (MBE) was studied by using the delta-doping technique. The segregation of Sb increases with increasing growth temperature and increasing Ge concentration of Si 1− x Ge x . This result is well explained by a two-state model in which the energy barrier to Sb surface segregation decreases with increasing Ge concentration of Si 1− x Ge x .

Molecular orbital theory was used to examine the improved gate oxide integrity of MOS (metal-oxide-semiconductor) devices against hot-hole injection; this improvement is associated with the incorporation of a nitrogen atom and subsequent incorporation of a fluorine atom. The bond dissociation energies of eight cluster models containing representative chemical bond environments in a modified oxide film – –Si–O–Si–, N(–Si–O–)– 3 , Si–N(–Si)–O–Si, Si–N(–O–Si) 2 , Si–N(–Si)–H, Si–F, Si–O–F, Si–N(–Si)–F – were extensively evaluated for both the neutral state and the hole-trapped state since the bond dissociation energy change is thought to be a relevant measure of bond durability against hot holes. A semiempirical molecular orbital program package, MOPAC, was used because of its short computational time. The applicability of MOPAC to the hole-trapped state was confirmed by comparing the MOPAC results with those obtained by first-principle calculations. The calculated changes in bond dissociation energy upon hole trapping imply that the improvement stems from the chemical bond formation of a silicon–nitride-like structure, N(–Si–O–)– 3 , in oxide bulk, and a Si–F structure in the Si/SiO 2 interfacial region. The synergetic effect of nitrogen and fluorine incorporation is most likely brought about by the formation of a Si 2 N–F structure in both the oxide and the interfacial region.

The mechanism for the stress-relaxation in the Ge condensation induced by H + irradiation-assisted oxidation method was investigated. Relaxation ratio of Si 0.7 Ge 0.3 (thickness: 28 nm) formed by medium dose H + irradiation (5 × 10 15 cm − 2 ) and oxidation at 1100 °C was limited to 35%. Post-annealing (1200 °C) improved this value significantly (70%), though defect density was found to be kept at low density ( 6 cm − 2 ). However, the height of cross hatches was increased (from 0.6 nm to 4.1 nm) after post-annealing. Based on these results, local-area slipping model was proposed, where slipping at SiGe/SiO 2 interface of local areas surrounded by cross hatches enhanced stress-relaxation. This model could quantitatively explain the stress-relaxation enhanced by combination of H + irradiation, oxidation-induced Ge condensation, and post-annealing.

Molecular beam epitaxy of the ferromagnetic silicide Fe 3 Si on Ge and Si substrates was investigated in a wide temperature range (60–400 °C). Epitaxial growth of Fe 3 Si layers was achieved on Ge (110), Ge (111), and Si (111) substrates. Especially, very low value (2.2%) of the minimum scattering yield in RBS measurements was obtained from Fe 3 Si layers, which were grown on Ge (111) at low temperature (60–130 °C) under the stoichiometric condition (Fe:Si = 3:1). Transmission electron microscopy measurements confirmed the formation of DO3-type Fe 3 Si and atomically flat interface between Fe 3 Si and Ge (111). In addition, thermal stability of Fe 3 Si was guaranteed up to 300 °C. Such high quality Fe 3 Si on Ge (111) substrates can be employed to realize Ge channel spin transistors, which can be integrated with Si large-scale integrated circuits.

Growth of ferromagnetic silicide Fe 3 Si on SiO 2 was investigated by using the molecular beam deposition technique. Measurements combined with X-ray diffraction and reflective high-energy electron diffraction clearly indicated that poly-crystal Fe 3 Si layers were formed on Si(111) substrates covered with thick (>2.7 nm) SiO 2 films. On the other hand, it is suggested that Fe 3 Si layers were epitaxially grown on Si(111) substrates covered with ultra-thin (1.3 nm) SiO 2 films. Transmission electron microscopy and electron diffraction measurements confirmed that single crystalline Fe 3 Si layers with (111) orientation were formed on Si(111) substrates with ultra-thin (1.3 nm) SiO 2 films. These results were considered to originate from heteroepitaxy on crystalline ultra-thin SiO 2 layer or lateral epitaxial growth over SiO 2 through pinholes.

Local strain evaluation was performed for single crystal Si pillar (SCSP) by micro Raman spectroscopy and photoluminescence (PL). SCSPs were fabricated by the mesa etching of Si-on-insulator followed by the etching of the buried oxide. The compressive strain was induced to SCSPs by SiN deposition using low-pressure chemical vapor deposition. The strain distribution was clearly observed in the plane of a certain pattern of SCSP. Strain ratio comparison was also performed for SCSPs with different shapes and sizes. Defect-related PL signals were also observed.

Influences of growth temperature on low-temperature (60-400 °C) molecular beam epitaxy of the ferromagnetic silicide Fe 3 Si layer on Ge substrates were investigated. X-ray diffraction and reflective high-energy electron diffraction measurements suggested that Fe 3 Si layers were epitaxially grown on Ge at a temperature between 60 and 300 °C, while another phase layer was epitaxially grown at 400 °C. Rutherford backscattering spectroscopy measurements revealed that Ge atoms began to diffuse into the Fe 3 Si layers above 300 °C, and the FeSiGe layer was formed at 400 °C. As a result, very low value (4.0%) of the minimum scattering yield (Χ min ) of the Fe 3 Si layers was obtained at 130 °C. Transmission electron microscopy measurements indicated that the interface of Fe 3 Si and Ge was atomically flat. In addition, analysis of the electron diffraction patterns of epitaxial Fe 3 Si layers confirmed the formation of D03-type Fe 3 Si.

Low-temperature (

The local strains in Si pillars induced by SiN stressors were quantitatively investigated as a function of geometry by micro-Raman scattering spectroscopy. Raman shifts of a cantilever microstructure were twice as large as those of a bridge microstructure. This difference was due to the different dimensions of the strains, i.e., biaxial strains in the cantilever type and uniaxial strains in bridge type. The thermal stability of the SiN stressor was also investigated. The results showed induced strains were stable after post-annealing at high temperature (∼1000 °C).

Direct formation of strained Si on insulator has been investigated by using laser annealing. The silicon on insulator (SOI) and amorphous Si layers deposited on SOI substrates were irradiated with an excimer laser. After the laser annealing, crystal Si layers with a strain of ∼0.6% were successfully formed on the buried oxide. Spectroscopic ellipsometry and atomic force microscopy measurements revealed the high crystallinity (∼100%) and small surface roughness (∼0.64 nm) of the formed layers. These results demonstrate that laser annealing technique will be a useful tool to fabricate strained Si on insulator without SiGe buffer layers.

Electrical properties of 50-nm-thick polycrystalline germanium (poly-Ge) films fabricated by pulsed laser annealing were investigated. Analysis of the electrical conductivity using a numerical calculation program revealed that the density of defect states at grain boundaries in the poly-Ge films was a low of 1.1 � 10 12 cm � 2 in contrast to a high density of 2.6 � 10 13 cm � 2 in the case of laser crystallized poly-Si films. Transient

Epitaxial growth of the ferromagnetic silicide Fe3Si on Si substrates was investigated using molecular beam epitaxy. X-ray diffraction (XRD) measurements revealed that the Fe3Si phase was formed at 60–300 °C, and the FeSi phase was formed at 400 °C. From the results of XRD and transmission electron microscopy measurements, it was found that the Fe3Si(111) layers were epitaxially grown on Si(111) substrates, while random poly-crystal Fe3Si layers were formed on Si(100) substrates. Detailed XRD measurements showed that a small amount of DO3-type Fe3Si was formed together with the B2-type Fe3Si. Vibrating sample magnetometer measurements revealed that Fe3Si(111) layers on Si(111) substrates have in-plane magnetic anisotropy with a period of 180°.

Ge surface segregation is a phenomenon in which Ge segregates to the epitaxial surface during MBE growth, and atomic hydrogen irradiation during MBE growth can reduce this phenomenon. To reveal the mechanism of both the phenomenon and the hydrogen irradiation effect, we have investigated the dependence of the phenomenon, with and without atomic hydrogen irradiation, on the Si growth rate, the substrate orientation, and the substrate temperature. The segregated Ge concentration does not depend exponentially on the Si growth thickness and a second-order reaction as well as a first-order reaction is necessary to describe the Ge segregation phenomenon in Si. The segregation length on Si(1 0 0) is larger than that on Si(1 1 1). This difference in segregation lengths appears to be due to a difference in the number of segregation paths in different substrates. Atomic hydrogen irradiation does not change the potential of the two-energy-state model, but it does change the probability of the second-order reaction occurring. As a result, the segregation is reduced.

The recent progress in Si heterostructure technologies is reviewed from physical and engineering viewpoints. Advanced methods to fabricate ultrashallow p-n junctions and high quality heterojunctions (SiGe/Si, μc-Si/SiC/Si) are developed to make a breakthrough in pushing back the limitation of Si-ULSI. Band engineering technology based on superstructures is also established by developing atomic hydrogen assisted molecular beam epitaxy. This opens up new expectations for Si-based optoelectronic integrated circuits. In addition, self-organized processing for nano-structure fabrication is being developed to realize new-concept quantum functional devices.

Modified metal-induced lateral crystallization (MILC) using a‐Ge∕a‐Si∕Ni∕SiO2 layered structures has been investigated. MILC growth velocity in the a‐Ge∕a‐Si layered structures was enhanced by three times compared with that in the a‐Si single layers. As a result, poly-Si films with large areas (∼10μm) were obtained in a short time annealing (