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406 results on '"Tsujino, S"'

2. Sub-nanosecond Electron Emission from Electrically Gated Field Emitting Arrays

Author

Paraliev, M., Tsujino, S., Gough, C., Kirk, E., and Ivkovic, S.

Subjects
Physics - Accelerator Physics
Abstract

Field Emitting Arrays (FEAs) are a promising alternative to the conventional cathodes in different vacuum electronic devices such as traveling wave tubes, electron accelerators and etc. Electrical gating and modulation capabilities, together with the ability to produce stable and homogeneous electron beam in high electric field environment are the key requirements for their practical application. Due to relatively high gate capacitance, fast controlling of FEA emission is difficult. In order to achieve sub-nanosecond, electrically controlled, FEA based electron emission a special pulsed gate driver was developed. Bipolar high voltage (HV)pulses are used to rapidly inject and remove charge form FEA gate electrode controlling quickly electron extraction gate voltage. Short electron emission pulses (<600 ps FWHM) were observed in low and high gradient (up to 12 MV/m) environment. First attempts were made to combine FEA based electron emission with radio frequency acceleration structures (1.5 GHz) using pulsed preacceleration. The gate driver design together with low inductance FEA chip contact system is described. The results obtained in low and high gradient experimental setups are presented and discussed., Comment: 4 pages, Proceeding : Pulsed Power Conference, Chicago, IL, 2011

Published
2011

3. Intra-valence-band mixing in strain-compensated SiGe quantum wells

Author

Tsujino, S., Borak, A., Falub, C., Fromherz, T., Diehl, L., Sigg, H., and Gruetzmacher, D.

Subjects
Condensed Matter - Other Condensed Matter, Condensed Matter - Materials Science
Abstract

We explore the midinfrared absorption of strain-compensated p-Si0.2Ge0.8/Si quantum wells for various well thicknesses and temperatures. Owing to the large band offset due to the large bi-axial strain contrast between the wells and barriers, the intersubband transitions energies from the ground state to the excited heavy hole (hh), light hole (lh) and split-off hole (so) states are resolved to ~0.5 eV. When hh2 is within ~30 meV of lh1 or so1 a partial transfer of the hh1-hh2 oscillator strength to the hh1-lh1 or hh1-so1 transitions is observed, which is otherwise forbidden for light polarized perpendicular to the plane of the wells. This is a clear sign of mixing between the hh and lh or so-states. A large temperature induced broadening of hh2 peak is observed for narrow wells indicating a non-parabolic dispersion of the hh2 states due to the mixing with the lh/so continuum. We found that the 6-band k.p theory gives a quantitative account of the observations. A possible role of many-body effects in the temperatureinduced negative peak shift is discussed., Comment: 16 pages, 3 figures

Published
2005
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4. Total Angular Momentum Conservation During Tunnelling through Semiconductor Barriers

Author

Gennser, U., Scheinert, M., Diehl, L., Tsujino, S., Borak, A., Falub, C. V., Grützmacher, D., Weber, A., Maude, D. K., Campidelli, Y., Kermarrec, O., and Bensahel, D.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We have investigated the electrical transport through strained p-Si/Si_{1-x}Ge_x double-barrier resonant tunnelling diodes. The confinement shift for diodes with different well width, the shift due to a central potential spike in a well, and magnetotunnelling spectroscopy demonstrate that the first two resonances are due to tunnelling through heavy hole levels, whereas there is no sign of tunnelling through the first light hole state. This demonstrates for the first time the conservation of the total angular momentum in valence band resonant tunnelling. It is also shown that conduction through light hole states is possible in many structures due to tunnelling of carriers from bulk emitter states., Comment: 4 pages, 4 figures

Published
2005
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20. Intersubband absorption of strain-compensated Si1-xGex valence-band quantum wells with 0.7<=x<=0.85.

Author

Fromherz, T., Medunňa, M., Bauer, G., Borak, A., Falub, C. V., Tsujino, S., Sigg, H., and Grützmacher, D.

Subjects
THIN films, SOLID state electronics, QUANTUM wells, OPTICS, PHYSICS, CRYSTAL growth
Abstract

Strain-compensated, p-type SiGe quantum wells with a high Ge concentration of up to 85% have been grown on commercially available Si0.5Ge0.5 pseudosubstrates by molecular-beam epitaxy. Structural investigations by transmission electron microscopy and high-resolution x-ray reflection and diffraction showed that at a growth temperature around T=300 °C, samples in excellent compliance with the design parameters, comparatively sharp interfaces, and negligible increase of growth-induced surface roughness can be grown. Comparison of polarization-dependent intersubband absorption measurements with simulated intersubband absorption spectra shows that for the quantum wells investigated in this work, the hole eigenstates, their in-plane dispersion, and the polarization-dependent intersubband transition matrix elements are accurately described by a strain-dependent, six-band k·p Luttinger-Kohn Hamiltonian in which only one fitting parameter—the intersubband transition linewidth—is used. [ABSTRACT FROM AUTHOR]

Published
2005
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22. Intersubband absorption of strain-compensated Si(sub 1-x)Ge(sub -x) valence-band quantum wells with 0.7 less than or equal to x less than or equal to 0.85

Author

Fromherz, T., Meduna, M., Bauer, G., Borak, A., Falub, C.V., Tsujino, S., Sigg, H., and Grutzmacher, D.

Subjects
Quantum theory -- Analysis, Eigenvalues -- Analysis, Molecular beams -- Research, Physics
Abstract

Strain-compensated, p-type SiGe quantum wells with a high Ge concentration of up to 85% was grown on commercially available Si(sub 0.5)Ge(sub 0.5) pseudosubstrates by molecular-beam epitaxy. Comparison of polarization-dependent intersubband absorption measurements with stimulated intersubband absorption spectra shows that for the quantum wells investigated, the hole eigenstates, their in plane dispersion and the polarization-dependent intersubband transition matrix elements are accurately described.

Published
2005

34. INTRA-ARTERIAL COMPA CHEMOTHERAPY FOR INVASIVE BLADDER CANCER

Author

Tsuyoshi Kobayashi, Masanori Kokuho, Tsujino S, Yamauchi T, Yuichi Tachibana, Tsuneo Kawai, and Sawano S

Subjects
Male, Oncology, medicine.medical_specialty, Vincristine, Ileus, Nausea, Urology, medicine.medical_treatment, Drug Administration Schedule, Cystectomy, Bleomycin, Peplomycin, Internal medicine, Antineoplastic Combined Chemotherapy Protocols, Humans, Infusions, Intra-Arterial, Medicine, Aged, Carcinoma, Transitional Cell, Chemotherapy, Bladder cancer, business.industry, Remission Induction, Infusion Pumps, Implantable, Middle Aged, medicine.disease, Surgery, Methotrexate, Transitional cell carcinoma, Urinary Bladder Neoplasms, Doxorubicin, Vomiting, Female, Cisplatin, medicine.symptom, business, medicine.drug
Abstract

We presented 12 patients with invasive bladder cancer treated by the subselective intra-arterial COMPA chemotherapy. COMPA was administered up to an average of 3.3 courses (ranged from 2 to 6 courses) every 2 or 3 weeks, consisting of cisplatin: 15 mg/M2 on days 4 and 5; vincristine (oncovin): 0.6 mg/M2 on days 1 and 2; methotrexate: 5 mg/M2 on days 2 and 3; peplomycin: 5 mg/body on days 1, 2 and 3; and adriamycin: 10 mg/M2 on day 4. These were injected through a teflon catheter the tip of which was placed just proximal to the aortic bifurcation, and another tip was led through a subcutaneous tunnel from the inguinally punctured area to the anterior chest wall. The 12 patients, 7 men and 5 women, ranged in age from 53 to 73 (mean: 67) years. Histopathologically 11 had transitional cell carcinoma and one had adenocarcinoma. Malignant gradings were grade 2 in 8 patients, and grade 3 in 4. The stagings were T2 in 3 patients, T3 in 5, T4 in 4 and only one had bony metastasis. Of the 12 patients, 10 were alive at the last follow-up with a mean duration of 36 months (range: 16 to 49). Six patients achieved a complete remission, four achieved a partial remission and two were stable. One died of ileus after 16 months and another of progression after 36 months. All the patients received post-chemotherapeutic adjunctive therapies, which were transurethral resection, partial cystectomy, radiation and/or intravesical instillation. The toxicities were not severe, but anorexia, nausea, vomiting, hair loss, numbness of fingers and/or toes, subileus, and leukopenia were noticed.(ABSTRACT TRUNCATED AT 250 WORDS)

Published
1992
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36. High temperature investigations of Si/SiGe based cascade structures using x-ray scattering methods

Author

Meduňa, M., Novák, J., Falub, C. V., Bauer, G., Tsujino, S., Grützmacher, D., Müller, E., Campidelli, Y., Kermarrec, O., Bensahel, D., and Schell, N.

Abstract

We have investigated strain compensated Si/Si0.2Ge0.8 multilayers, which were grown pseudomorphically on relaxed Si0.5Ge0.5 pseudosubstrates by molecular beam epitaxy. The stability of these highly strained Si/SiGe structures upon in situ annealing has been measured by means of x-ray reflectivity (XRR) up to 830°C. The temporal evolution of XRR reciprocal space maps was recorded, and a gradual disappearance of the multilayer structure was detected after annealing for 7 h at a temperature of 790°C. From the temporal evolution of the optical constants of the layers, deduced from the simulations and fits of the specular reflectivity, we obtained an interdiffusion coefficient D = (1.01 ± 0.03) × 10-21 m2 s-1 at 790°C.

Published
2005

38. Electron beam collimation with a 40 000 tip metallic double-gate field emitter array and in-situ control of nanotip sharpness distribution

Author

Helfenstein, P, Guzenko, V A, Fink, H W, Tsujino, S, Helfenstein, P, Guzenko, V A, Fink, H W, and Tsujino, S

Abstract

The generation of highly collimated electron beams from a double-gate field emitter array with 40000 metallic tips and large collimation gate apertures is reported. Field emission beam measurements demonstrated the reduction of the beam envelope down to the array size by applying a negative potential to the on-chip gate electrode for the collimation of individual field emission beamlets. Owing to the optimized gate structure, the concomitant decrease of the emission current was minimal, leading to a net enhancement of the current density. Furthermore, a noble gas conditioning process was successfully applied to the double-gate device to improve the beam uniformity in-situ with orders of magnitude increase of the active emission area. The results show that the proposed double-gate field emission cathodes are promising for high current and high brightness electron beam applications such as free-electron lasers and THz power devices.

Published
2013

39. Fabrication of metallic double-gate field emitter arrays and their electron beam collimation characteristics

Author

Helfenstein, P, Jefimovs, K, Kirk, E, Escher, C, Fink, H-W, Tsujino, S, Helfenstein, P, Jefimovs, K, Kirk, E, Escher, C, Fink, H-W, and Tsujino, S

Abstract

The fabrication of double-gate metallic field emitter arrays with large collimation gate apertures and their field emission beam characteristics are reported. The device fabrication steps, including the molding technique for array fabrication, the electron extraction gate fabrication by the self-aligned resist etch-back method, and the fabrication of the collimation gate electrode using a focused ion beam assisted method are described in detail. The experimental results of 2 × 2 tip arrays with the proposed double-gate structure demonstrate an order of magnitude enhancement in beam brightness with minimal current loss. A similarly high beam brightness enhancement was achieved with a 20 × 20 tip array device, showing the scalability of the proposed structure. The observation of improved current-voltage characteristics with the 20 × 20 tip array is ascribed to the difference in gate aperture shape. The possibility of further improving the beam characteristics of double-gate field emitter arrays and the reduction of the transverse electron velocity spread are discussed.

Published
2012

40. Highly collimated electron beams from double-gate field emitter arrays with large collimation gate apertures

Author

Helfenstein, P, Kirk, E, Jefimovs, K, Vogel, T, Escher, C, Fink, H W, Tsujino, S, Helfenstein, P, Kirk, E, Jefimovs, K, Vogel, T, Escher, C, Fink, H W, and Tsujino, S

Abstract

Electron collimation in field emitter arrays with electron extraction gate and collimation gate electrodes is studied with the goal to develop a high-brightness high current cathode. Using metallic field emitter arrays prepared by the molding method, we fabricated a stacked double-gate device with the two gates differing in diameter by a process utilizing focused-ion beam milling. We measured the field-emission beam characteristics and demonstrated a reduction of the emission angle by a factor of 7.1±0.8 with minimal emission current decrease under collimating conditions, resulting in a current density increase by a factor of 13.9±1.0.

Published
2011

41. Field-emission characteristics of molded molybdenum nanotip arrays with stacked collimation gate electrodes

Author

Tsujino, S, Helfenstein, P, Kirk, E, Vogel, T, Escher, C, Fink, H-W, Tsujino, S, Helfenstein, P, Kirk, E, Vogel, T, Escher, C, and Fink, H-W

Abstract

Double-gate field-emission characteristics of metallic field-emitter-array (FEA) cathodes fabricated by molding with stacked collimation gate electrodes with planar end plane are reported. The collimation of field-emission electron beam with minimal reduction of emission current is demonstrated when a negative bias is applied to the collimation gate, whereas when the two electrodes are at the same potential, the emission characteristic of the double-gate device is the same as that of the single-gate device that shows an emission current of ~1 mA from 40 × 40 tip arrays. Results indicate that the device structure of the fabricated double-gate FEAs is promising for high-brilliance cathode applications

Published
2010

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