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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3319-3325 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Mulliken electron population analysis has been a standard feature of computer output from the quantum mechanical molecular calculation. An extension of the original analysis is proposed here. It produces a point-charge model of a molecule that retains the same electric dipole moment as calculated with the molecular wave function. The analysis offers visually more interesting information than the original Mulliken analysis. The extension can be made easily by extracting and printing out some additional numerical data usually once computed but discarded after being processed in molecular calculations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2093-2105 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Models capturing the periodic steady-state behavior of rf capacitively coupled discharges are now commonplace. New plasma sources have been motivated by selectivity, charge-damage mitigation, and general process control needs in plasma processing of electronic materials. These new sources require models that can accurately capture the transient behavior of the plasma source. Such models are not commonplace because the behavior of transport parameters in transients is still not well understood and because the problem is inherently stiff, i.e., widely disparate time scales are important. In this paper, we present the results of an investigation of the simplest type of transient, known as a step disturbance, in a 2 cm gap parallel-plate argon discharge at 1 Torr. As examples, two classes of step transients are considered: step increases in the peak-to-peak (pp) applied voltage (300 to up to 450 V pp) and step decreases (300 to as low as 150 V pp). The resulting transients are interpreted in terms of time scales representative of electron and ion motion in the sheath, ionization dynamics, and neutral transport processes. The possibility of using these transients as a means of process identification is discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2844-2848 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microscanning electron microscope (SEM) column has been constructed as an attachment of an ultrahigh-vacuum chamber with a 70 mm diam flange to observe microstructures on a solid surface. The micro-SEM column is 26 mm diam and 140 mm long and operated in an energy range from 100 eV to 3 keV. It consists of a thermal-field-emission (TFE) gun and two magnetic lenses. The excitation of the objective lens for 3 kV electrons is 250 A T at a working distance of 10 mm. The saturated temperature of the objective lens at the excitation of 250 A T is approximately 50 °C and the vacuum of the chamber is 2×10−10 Torr. The electron probe is adjustable against a specimen position from the outside of the vacuum by movement of the SEM column with screws. The spot size of the electron probe is 100 A(ring) at 3 kV and 3000 A(ring) at 300 eV in conditions of a working distance of 10 mm and a probe current of 3×10−11 A.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3475-3477 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Secondary electron yields depending on work function were measured for 30 species of metal in ultrahigh vacuum by electron and ion bombardment. Secondary electron yields induced by electrons at 10 keV increase with work function, while those by Ar+ ions at 3 keV decrease with increasing work function. The opposite dependencies of secondary electron yields on work function between electron and ion bombardment are discussed on the basis of the different mechanisms of secondary electron emission, i.e., kinetic and potential emission for electron and ion bombardment, respectively. © 2000 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 611-613 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The contrast of the secondary electron images in scanning ion microscopy (SIM) is compared with that in scanning electron microscopy (SEM) with ultrahigh vacuum for Al, Cu, Ag, and Au metals deposited on the Si(100) clean surface. The order of the secondary electron yields as a function of the atomic number (Z2) for ion bombardment is opposite to that for electron bombardment. The brightness of the secondary electron images observed by a focused Ga+ ion beam at 30 keV decreases with increasing Z2, while that by the electron beam increases with Z2. On the other hand, the order of the total secondary ion yields in SIM increases with Z2. The secondary electron image observed by a focused Ar+-ion beam at 3 keV shows the similar contrast to that of the Ga+-ion beam. The different Z2 dependence of the secondary electron yields between SEM and SIM was quantitatively confirmed by the total secondary electron spectra and is discussed based on the range profile below the surface, and it is concluded that the decrease of the secondary electron yields in SIM is attributed to the increase of the reflected ions at the surface with increasing Z2. © 1998 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2333-2335 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple and sensitive detection method of Xe(1s5) excited atoms in the vicinity of a discharge wall with laser-collision induced fluorescence (LCIF) produced by evanescent wave absorption is proposed. The signal to noise (S/N) ratio was 102. The hyperfine structure (hfs) in the Xe LCIF spectra induced by resonant absorption of Xe(1s5→2p6) was confirmed to be identical with the hfs in laser absorption spectra, although the detection point (xPD) on the discharge wall was chosen independently of the position of the EW absorption (xEW). The insignificantly large fluorescence, which appeared for incident light angles to a prism larger than 4.8°, is explained by the fact that the refracted light emerged in a plasma. The Xe(1s5) number density in a dc Xe discharge, although roughly estimated, on the tube wall between the electrodes is presented. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1848-1858 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transient response of electronegative radio-frequency glow discharges is important for process control, charge free etching, and highly selective etch applications. The step response of typical electronegative process gases (silane at 1 Torr and chlorine at 100 mTorr) is studied using a drift-diffusion model for silane and a three-moment model for chlorine. The silane simulations include a blocking capacitor whereas the chlorine results do not. For the silane results with a blocking capacitor in series with the plasma, it is found that there are three types of transients. Depending on the final steady-state value of the source rf voltage, the step response can be characterized either by smooth transitions in the number densities of species in the discharge from one steady state to the next, temporary extinction of the discharge or a discharge mode characterized by temporary extinction and reignition of the discharge. In the case of silane definite thresholds separate the phenomena. The step response of the chlorine discharges is always characterized by a smooth transition from one steady state to the next. Smooth transitions from one steady state to the next in the case of step decreases in the source voltage are possible since decrease of the negative ion density in the bulk is controlled by ion–ion recombination. It appears that the temporary extinction of the discharge and natural pulsed steady state is the consequence of how the voltage is divided between the gap and the blocking capacitor during the transient and the fact that the attachment coefficient becomes larger than the ionization coefficient at low values of reduced electric field. © 1998 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1146-1155 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge damage considerations are prompting the development of neutral beam sources for etching applications. Anisotropic etching with hyperthermal Cl2 and SF6 beams has been demonstrated. We describe a two-dimensional plasma chemistry fluid model of laser ablation of frozen Cl2 in vacuum as a neutral beam source. In this scheme an externally applied electric field would be used to enhance the dissociation rate of Cl2 potentially providing an enhanced Cl content in the beam for a greater etch rate. Laser ablation generated neutral beams also may contain a desirable and controllable ion content which may be used to further enhance the etch rate. Limitations of the concept are discussed. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 472-473 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature cw operation of an InGaAs/InGaAsP multiple quantum well (MQW) laser diode on a Si substrate is reported. The MQW laser emits at a 1.54 μm wavelength and exhibits no degradation after over 2000 h of operation. Employing a hybrid organometallic vapor phase epitaxy/vapor mixing epitaxy method and a layer structure for improving crystalline quality, high-quality MQW layers are obtained. A stable longitudinal mode spectrum demonstrates the effectiveness of the MQW active layer.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2965-2967 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A wire-conductor fabrication method has been developed for Cu–Ag alloys containing 2–60 at. % Ag where high strength and high conductivity conductors are obtained by cold working combined with intermediate heat treatment. The intermediate heat treatment is repeated 3–4 times at 350–450 °C for 1–2 h at appropriate stages of reduction of area. The optimized Cu-16 at. % Ag alloy wire with 99% reduction of area showed a tensile strength of 1000 MPa and an electrical conductivity of 80% IACS at room temperature. This suggests that the wires fabricated may be very promising for high-field pulsed magnet use.
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