- Email: [email protected]
Ionized-cluster beam deposition
Classified abstracts 1619-1628
Teflon than does silver for the specimens tested and that the failure modes for these two metal-dielectric interfaces are substantially different. The shearing stresses required to remove the films from their substrates have been calculated and are in close agreement with previously reported data on rigid substrates. L F Goldstein and T J Bertone, J Vac Sci Technol, 12 (6), 1975, 1423-1426. 3O 1619. Activation of filamentary field emitters by growing microneedles of tungsten. (USA) It was attempted to grow microneedles of tungsten on 10-~.m-diam tungsten wires for the purpose of preparing emitters of high efficiency for field-ionization mass spectrometry. A large quantity of tungsten needles with dendritic structures was successfully grown by reducing vapor-deposited tungsten oxide with 1-5 × 10 -2 tort hydrogen while applying a positive potential of 5-6 kV. The needle growth occurred in a critical manner when deposited tungsten oxide attained a temperature of ---1200 K, and needles obtained were thin enough to easily generate high electric fields of 107-10 s V/cm. Testing in a mass spectrometer actually verified that the needles can yield fieldionization mass spectra of satisfactory quality for typical organic substances. (Japan) Fumio Okuyama, J Vac Sci Technol, 12 (6) 1975, 1399-1402. 30 1620. Evaporation of metal from a covered source. (France) When metal is evaporated in an open crucible an uneven surface with projections is often formed. This is unacceptable for many magnetic or electronic thin film applications. Fault-free metal surfaces can be produced by slow evaporation but this is time-consuming and requires vacuum. A more simple, efficient method is described using a combustion boat of refractory metal with a curved, tight-fitting cover. The cover has a small hole which allows metal vapour to escape. The method can be used for the deposition of metal on electrodes. The source lasts for 50 evaporations of copper on average. R D Mathis et al, Vide, 30 (177-178), 1975, 153-154 (in French).
31. SPUTTERING 31 1621. Ionized-cluster beam deposition. (USA) We describe a form of deposition in which material is vaporized in a crucible and the vapor then ejected through a fine nozzle at the focus of an electron beam in a high vacuum. The vapor, on emerging from the nozzle, is partially condensed into clusters that are ionized by electron bombardment and then accelerated onto the substrate. The deposited films show good adhesion and large crystallite size. Examples include the deposition of Cu onto glass, Si onto Si, and ZnS onto NaCI. (Japan) T Takagi et al, J Vac Sci Technol, 12 (6), 1975, 1128-1134. 31 1622. Novel mictofabrieafion process. (USA) A process for fabricating metallic microstructures having submicron dimensions is discussed. Based on simple electrochemical etching of sputtered metallic strips on substrates, the process is potentially useful for making mechanically stable point-contact devices. S M Faris and T K Gustafson, J Vac Sci Technol, 12 (6), 1975, 13561358. 31 1623. Electron microprobe analysis of thin films with reference to "semi-thin" deposits (0.5-1/~m) of Cd, Hg~_= Te. (France) Quantitative and qualitative investigation of many deposits of the type Cd= Hgl-= Te (where x - - 0.2) by electron microprobe analysis is described. Deposits of several thousand Angstroms to I micron thick are prepared by cathodic sputtering in a mercury atmosphere on Si or Cd Te substrates. The most important factor responsible for the localisation of ionisation phenomena which determines the maximum intensity of x is found to be the acceleration tension of the electron beam. The most suitable film thickness for analysis is 5000 A. For thinner films equipment working at less than 6 kV and with more sensitive receptors is required. C Bahezre, Vide, 30 (179), 1975, 186-190 (in French) 31 1624. An investigation of ion etching. (Netherlands) With ion etching it is possible, for the same etch depth of, say, 1 pro, to form patterns with lateral dimensions (also 1 pm) that are approx214
imately five times smaller than is possible with conventional chemical etching methods. Two currently practised ion-etching processes are r.f. cathode sputtering and ion-beam etching. Research carried out at Philips Forschungs-laboratorium Hamburg, has led to the following conclusions: back-diffusion must be avoided as far as possible (which means that the ion-beam process will often be the most suitable method); the required ratio of etch rates (low for the mask, high for the substrate) can be achieved very effectively with a titanium mask and etching in an argon and oxygen atmosphere; sputtering must depend as little as possible on the angle of incidence of the ions. With regard to this last point, titanium is again found to be an excellent mask material. The best results are obtained with a titanium mask and bombardment at an oblique angle. (Germany) H Dimigen and H Lfithje, Philips Tech Rev, 35 (718), 1975, 199-208. 31 1625. Ceramic-to-metal bonding with sputtering as a metallization technique. (Netherlands) Sputtering has proved to be a valuable procedure for metallizing ceramics for subsequent brazing. The metal coating should consist of three separate layers. The first is a metal that has a high oxygen atfmity; this layer provides the adhesion between the coating and the ceramic. A second layer protects the first from being attacked by the molten braze metal. If necessary, a third layer can be applied as a protection against oxidation and to promote wetting of the coating during brazing. Ceramic-to-metal seals produced with this metallization technique give excellent vacuum sealing and have a mechanical strength that is not limited by the mechanical properties of the braze-metal joint. (USA) R L Bronnes et al, Philips Tech Rev, 35 (7/8), 1975, 209-211. 33. NUCLEONICS 33 1626. Two-dimensional ion effects in relativistic diodes. (USA) In relative diodes, ions are emitted from the anode plasma. The effects and properties of these ions are studied via a two-dimensional particle simulation code. The space charge of these ions enhances the electron emission, and this additional current (including that of the ions themselves) aids in obtaining superpinched electron beams for use in pellet fusion studies. J W Ponkey, J Vac Sci Technol, 12 (6), 1975, 1214--1217. 33 1627. Progress in intense pulsed ion sources. (USA) Progress in the development of intense, pulsed ion sources is described. The major impediment, electron breakdown, can be solved by magnetic insulation of the accelerating gap or reflex geometries. Both magnetic insulation and the reflex triode have been used successfully at Cornell to efficiently generate multikiloampere ion fluxes. Scaling of these devices to the range of parameters attained by pulsed electron machings (MA in the MV range) appears feasible. Such ion beams may have applications in plasma heating, ion ring production, thermonuclear pellet compression, and other areas of physical research. S Humphries, J Vac Sci Technol, 12 (6), 1975, 1204-1207. 33 1628. L A M P F experimental-urea bt-am current monitors. (USA) This paper summarizes the design and operational performance of a wide-range current monitor system used to measure charged-particle currents in the experimental areas of the Clinton P. Anderson Meson Physics Facility (LAMPF), a proton acceleratbr. The major features of the system are high sensitivity, wide dynamic range, and the ability to withstand high levels of radiation. The current pulses detected are from 50 ~ to 1 ms in duration at repetition rates of from 1 to 120 Hz. The pulse amplitude varies from l p A to 17 mA of protons or H - ions. Both real-time and integrated outputs are available, and the minimum detectable currents are I t~A at the video output and 50 nA at the integrated output. The basic system is comprised of toroids, preamplifiers, signal conditioners, voltage-tofrequency converters, and digital accumulators. The entire system is spread out over 1 km of beam pipe. Provision is made for calibration and for sending the outputs to remote users. The system is normally controlled by a small digital computer, which allows the system to be quite flexible in operation. The design features of the toroids and the associated electronics are discussed in detail, with emphasis on
Teflon than does silver for the specimens tested and that the failure modes for these two metal-dielectric interfaces are substantially different. The shearing stresses required to remove the films from their substrates have been calculated and are in close agreement with previously reported data on rigid substrates. L F Goldstein and T J Bertone, J Vac Sci Technol, 12 (6), 1975, 1423-1426. 3O 1619. Activation of filamentary field emitters by growing microneedles of tungsten. (USA) It was attempted to grow microneedles of tungsten on 10-~.m-diam tungsten wires for the purpose of preparing emitters of high efficiency for field-ionization mass spectrometry. A large quantity of tungsten needles with dendritic structures was successfully grown by reducing vapor-deposited tungsten oxide with 1-5 × 10 -2 tort hydrogen while applying a positive potential of 5-6 kV. The needle growth occurred in a critical manner when deposited tungsten oxide attained a temperature of ---1200 K, and needles obtained were thin enough to easily generate high electric fields of 107-10 s V/cm. Testing in a mass spectrometer actually verified that the needles can yield fieldionization mass spectra of satisfactory quality for typical organic substances. (Japan) Fumio Okuyama, J Vac Sci Technol, 12 (6) 1975, 1399-1402. 30 1620. Evaporation of metal from a covered source. (France) When metal is evaporated in an open crucible an uneven surface with projections is often formed. This is unacceptable for many magnetic or electronic thin film applications. Fault-free metal surfaces can be produced by slow evaporation but this is time-consuming and requires vacuum. A more simple, efficient method is described using a combustion boat of refractory metal with a curved, tight-fitting cover. The cover has a small hole which allows metal vapour to escape. The method can be used for the deposition of metal on electrodes. The source lasts for 50 evaporations of copper on average. R D Mathis et al, Vide, 30 (177-178), 1975, 153-154 (in French).
31. SPUTTERING 31 1621. Ionized-cluster beam deposition. (USA) We describe a form of deposition in which material is vaporized in a crucible and the vapor then ejected through a fine nozzle at the focus of an electron beam in a high vacuum. The vapor, on emerging from the nozzle, is partially condensed into clusters that are ionized by electron bombardment and then accelerated onto the substrate. The deposited films show good adhesion and large crystallite size. Examples include the deposition of Cu onto glass, Si onto Si, and ZnS onto NaCI. (Japan) T Takagi et al, J Vac Sci Technol, 12 (6), 1975, 1128-1134. 31 1622. Novel mictofabrieafion process. (USA) A process for fabricating metallic microstructures having submicron dimensions is discussed. Based on simple electrochemical etching of sputtered metallic strips on substrates, the process is potentially useful for making mechanically stable point-contact devices. S M Faris and T K Gustafson, J Vac Sci Technol, 12 (6), 1975, 13561358. 31 1623. Electron microprobe analysis of thin films with reference to "semi-thin" deposits (0.5-1/~m) of Cd, Hg~_= Te. (France) Quantitative and qualitative investigation of many deposits of the type Cd= Hgl-= Te (where x - - 0.2) by electron microprobe analysis is described. Deposits of several thousand Angstroms to I micron thick are prepared by cathodic sputtering in a mercury atmosphere on Si or Cd Te substrates. The most important factor responsible for the localisation of ionisation phenomena which determines the maximum intensity of x is found to be the acceleration tension of the electron beam. The most suitable film thickness for analysis is 5000 A. For thinner films equipment working at less than 6 kV and with more sensitive receptors is required. C Bahezre, Vide, 30 (179), 1975, 186-190 (in French) 31 1624. An investigation of ion etching. (Netherlands) With ion etching it is possible, for the same etch depth of, say, 1 pro, to form patterns with lateral dimensions (also 1 pm) that are approx214
imately five times smaller than is possible with conventional chemical etching methods. Two currently practised ion-etching processes are r.f. cathode sputtering and ion-beam etching. Research carried out at Philips Forschungs-laboratorium Hamburg, has led to the following conclusions: back-diffusion must be avoided as far as possible (which means that the ion-beam process will often be the most suitable method); the required ratio of etch rates (low for the mask, high for the substrate) can be achieved very effectively with a titanium mask and etching in an argon and oxygen atmosphere; sputtering must depend as little as possible on the angle of incidence of the ions. With regard to this last point, titanium is again found to be an excellent mask material. The best results are obtained with a titanium mask and bombardment at an oblique angle. (Germany) H Dimigen and H Lfithje, Philips Tech Rev, 35 (718), 1975, 199-208. 31 1625. Ceramic-to-metal bonding with sputtering as a metallization technique. (Netherlands) Sputtering has proved to be a valuable procedure for metallizing ceramics for subsequent brazing. The metal coating should consist of three separate layers. The first is a metal that has a high oxygen atfmity; this layer provides the adhesion between the coating and the ceramic. A second layer protects the first from being attacked by the molten braze metal. If necessary, a third layer can be applied as a protection against oxidation and to promote wetting of the coating during brazing. Ceramic-to-metal seals produced with this metallization technique give excellent vacuum sealing and have a mechanical strength that is not limited by the mechanical properties of the braze-metal joint. (USA) R L Bronnes et al, Philips Tech Rev, 35 (7/8), 1975, 209-211. 33. NUCLEONICS 33 1626. Two-dimensional ion effects in relativistic diodes. (USA) In relative diodes, ions are emitted from the anode plasma. The effects and properties of these ions are studied via a two-dimensional particle simulation code. The space charge of these ions enhances the electron emission, and this additional current (including that of the ions themselves) aids in obtaining superpinched electron beams for use in pellet fusion studies. J W Ponkey, J Vac Sci Technol, 12 (6), 1975, 1214--1217. 33 1627. Progress in intense pulsed ion sources. (USA) Progress in the development of intense, pulsed ion sources is described. The major impediment, electron breakdown, can be solved by magnetic insulation of the accelerating gap or reflex geometries. Both magnetic insulation and the reflex triode have been used successfully at Cornell to efficiently generate multikiloampere ion fluxes. Scaling of these devices to the range of parameters attained by pulsed electron machings (MA in the MV range) appears feasible. Such ion beams may have applications in plasma heating, ion ring production, thermonuclear pellet compression, and other areas of physical research. S Humphries, J Vac Sci Technol, 12 (6), 1975, 1204-1207. 33 1628. L A M P F experimental-urea bt-am current monitors. (USA) This paper summarizes the design and operational performance of a wide-range current monitor system used to measure charged-particle currents in the experimental areas of the Clinton P. Anderson Meson Physics Facility (LAMPF), a proton acceleratbr. The major features of the system are high sensitivity, wide dynamic range, and the ability to withstand high levels of radiation. The current pulses detected are from 50 ~ to 1 ms in duration at repetition rates of from 1 to 120 Hz. The pulse amplitude varies from l p A to 17 mA of protons or H - ions. Both real-time and integrated outputs are available, and the minimum detectable currents are I t~A at the video output and 50 nA at the integrated output. The basic system is comprised of toroids, preamplifiers, signal conditioners, voltage-tofrequency converters, and digital accumulators. The entire system is spread out over 1 km of beam pipe. Provision is made for calibration and for sending the outputs to remote users. The system is normally controlled by a small digital computer, which allows the system to be quite flexible in operation. The design features of the toroids and the associated electronics are discussed in detail, with emphasis on