Showing papers by "Varian Associates published in 1995"

Magnetron sputtering source for low pressure operation

Abstract: A magnetron sputtering source which is capable of very low pressure operation is disclosed. The source comprises a dish-shaped sputter target behind which is mounted a primary magnet for confining a plasma discharge adjacent to the front surface of the sputter target. A bucking magnet, positioned adjacent to the perimeter of the sputter target and, preferably, at the same level as the target, is used to prevent the magnetic field created by the primary magnet from spreading out at near the edge of the sputter target. This enables the source to operate at very low pressure and reduces the impedance of the discharge.

Dual-frequency capacitively-coupled plasma reactor for materials processing

Abstract: The present invention is directed to a dual frequency capacitively-coupled plasma apparatus for materials processing. According to a first aspect of the present invention, a dual frequency triode reactor includes a VHF (30-300 MHz) RF power supply capacitively coupled to an upper reactor electrode and an HF (0.1-30 MHz) RF power supply capacitively coupled to a lower reactor electrode to which the wafer is attached. The VHF power supply is used to generate and control formation of a low sheath potential, high density plasma for minimum device damage and rapid etching/deposition while the HF power supply is used to provide a DC bias to the wafer substrate. According to a second aspect of the present invention, a tailored, powered upper electrode, at least a portion of which is generally conical in shape, is employed to provide a uniform etch across the diameter of the wafer.

High performance turbomolecular vacuum pumps

Abstract: Turbomolecular vacuum pumps having structures which provide increased pumping speed, increased discharge pressure and decreased operating power in comparison with prior art turbomolecular vacuum pumps. In a first embodiment, the stators of one or more axial flow vacuum pumping stages in proximity to the exhaust port of the vacuum pump have progressively lower conductance so that the bulk velocity of the gas being pumped is increased. In a second embodiment, one or more stages near the inlet port of the vacuum pump are provided with a peripheral channel to utilize the centrifugal component of the gas being pumped. In a third embodiment, one or more stages in the vacuum pump are molecular drag stages, each including a disk rotor. One or more pumping channels in the stator adjacent to the upper surface of the disk are connected in series with one or more pumping channels adjacent to the lower surface of the disk. In a fourth embodiment, one or more stages of the vacuum pump are regenerative stages, each including a regenerative impeller. Pumping channels in the upper and lower portions of the stator are connected in series. The stator channels can be provided with fixed, spaced-apart ribs for improved performance.

Apparatus for and method of forming a parallel ion beam

Abstract: A time-of-flight mass spectrometer includes an ion beam source having a quadrupole ion trap. To form a parallel ion beam, the ions are simultaneously sucked and pulsed out of an interaction region of the trap through an opening in a front end cap electrode of the trap by applying different polarity voltage pulses at the same time to the front end cap electrode and a back end cap electrode of the trap.

High displacement rate,scroll-type, fluid handling apparatus

Abstract: A positive displacement fluid handling apparatus has a first, high volumetric displacement rate scroll pump of nested interacting pairs of fixed and movable spiral-shaped blades supported in a housing between an inlet and an outlet. Each adjacent blade pair is of sufficient angular extent, preferably only about 360°, to close an inter-blade pocket. In a preferred form for a vacuum pump, a second scroll pump mounted in the housing has its fluid inlet in direct fluid communication with the first scroll outlet. The second scroll has a single pair of co-acting fixed and movable blades with multiple revolutions with a relatively short axial height. The low back leakage of this second pump allows the first pump to omit tip seals on the free spiral edges of the blades. The volumetric displacement rate of the first pump exceeds that of the second pump. An orbiting plate carries the movable blades of both scroll pumps. The drive has a small crank radius which reduces seal velocity and wear, and reduces radial crank force. Ball thrust bearings held between recesses in the periphery and in the plate offset axially directed compressive forces while synchronizing the orbiting movement. A fan mounted on the drive air cools the apparatus. There is no oil or other liquid lubricant or coolant exposed to the working fluid.

Nuclear magnetic resonance receiver, method and system

Abstract: An NMR receiver includes an analog to digital converter for sampling a nuclear magnetic resonance probe output signal at a frequency that is less than the probe signal center frequency and is at least twice the probe signal bandwidth.

Phonon anomalies at the magnetic phase transition in SrRuO3.

Abstract: Raman spectra of ${\mathrm{SrRuO}}_{3}$ films grown epitaxially on ${\mathrm{LaAlO}}_{3}$ substrate by a pulsed laser deposition have been measured Phonon spectra showed an anomalous temperature dependence in the range of the magnetic phase transition indicating strong spin-lattice interaction No sharp magnon lines were observed, but the broad continuum spectrum showed redistribution of intensity at the magnetic phase transition suggesting that multimagnon processes may contribute to the continuum

A method of space charge control in an ion trap mass spectrometer

Abstract: A method of using a quadrupole ion trap mass spectrometer (10) for high resolution mass spectroscopy is disclosed. In the preferred embodiment, the space charge in the ion trap is controlled with high accuracy. The mass spectrum to be analyzed is divided into a plurality of contiguous segments (s1, s2, s3...) and each of the segments is separately scanned. To control space charge, a broadband supplemental waveform (Vs) is applied to the ion trap (1) during the ionization period (Ts1, Ts2, Ts3...) for each segment, the broadband signal being constructed to eliminate all unwanted ions from the ion trap by resonance ejection such that only those ions having masses within the desired mass segment remain in the trap. Preferably, the ionization of each mass segment is performed under identical trapping conditions, and the ionization parameters for each segment is adjusted to optimize the space charge in the trap for that particular segment. Conveniently, the adjustment of ionization parameters may be based on the previous analytical scan of the same mass segment.

Apparatus and method for temperature control of workpieces in vacuum

Abstract: A flat workpiece (2) is placed in contact with a flat platen in a vacuum chamber, and is held by a uniformly-distributed force while a small mass flow of gas is introduced along a contour (203) to form a uniform pressure region between the flat workpiece (201) and the platen (2). Separation of the two surfaces due to surface roughness is less than the gas mean free path, and high rates of heat transfer are obtained uniformly over the area of the workpiece (2). A scavenging port (207), located outwardly of the gas introduction contour (203) is differentially pumped to reduce the rate of gas leakage into the chamber. Pressure is provided by an electrostatic clamp (250) where the voltage activation sequence prevents workpiece vibration. A clamping current sensor immediately detects degree of contact, e.g., due to debris on the platen, and initiates a suitable warning or control.

Method and device for vibration during solid phase microextraction

Abstract: An apparatus is described for carrying out solid phase microextraction and analysis of analytes in a fluid carrier in which a fiber within a housing is vibrated by a vibrating means during microextraction. The housing contains access means so that the carrier and analytes can be brought into contact with the vibrating fiber during the extraction stage. In a preferred embodiment of the present invention, the vibrating means comprises a membrane, a solenoid for vibrating the membrane, a frame, a retainer mounted on the frame for holding the solenoid, a holder for the membrane, and a retainer arm having one end connected to the retainer and the other end attached to the holder. A method for microextraction and analysis is also described in which a vibrating fiber is placed into contact with analytes to be analyzed in a suitable carrier deposited in a container for a sufficient period of time for microextraction to occur. Subsequently the fiber is removed and placed into a suitable analytical instrument for desorption and analysis with respect to at least one component on the fiber.

Analysis of creep transients in pure metals following stress changes

Abstract: The analysis of creep transients associated with stress change tests is reviewed, with an emphasis on using the results of these experiments to characterize the kinetics of deformation under conditions of nominally constant structure. In order to develop a common framework for the description of results obtained by various authors, operational definitions of the characteristic strain rates observed after stress changes are adopted. The data for aluminum reported by numerous investigators provide a consistent picture over a broad range of temperatures and initial creep stresses. These results show that transient creep after stress reductions occurs by two parallel processes of dislocation glide within subgrain interiors and dynamic recovery associated with subgrain boundary migration. Following relatively large stress reductions, the creep transient is dominated by the subgrain boundary migration processes. After relatively small changes in stress, thermally activated motion of dislocations within subgrain interiors is the predominant mechanism of deformation. In this regime, the creep transients can be described by a thermally activated rate law, thereby enabling various activation parameters to be evaluated from the data. In particular, the true activation areas are found to be equal to the dislocation spacing within subgrain interiors, hence are consistent with thermally activated cutting of forest dislocations. Limited results for other f.c.c. metals and related materials are shown to follow the trends established for aluminum. In particular. it is demonstrated that the data for pure copper and LiF at high temperatures and after small stress changes are also consistent with a description based on thermally activated glide. However, the true activation areas in copper are about five times greater than the dislocation spacing. This difference between copper and aluminum is attributed to the fact that the former has a substantially lower stacking fault energy. It is argued that the resulting wider separation of partials makes the thermally activated cutting of forest dislocations more difficult.

Development of low loss IR transmitting chalcogenide glass fibers

Abstract: We have fabricated long lengths of low loss sulphide and telluride glass fibers for the 1 - 6 and 3 - 12 micrometers regions, respectively. Minimum losses for core/clad fibers are approximately 0.6 and 0.7 dB/m, respectively, while core-only fibers have exhibited losses of about 0.1 dB/m. The measurements have been performed on long lengths, typically 7 - 50 meters. Fiber strengths are reasonable for many short length applications, but improved processing will lead to stronger fibers for long length applications. These fibers are candidates for chemical sensors and for IR laser power delivery.

Frequency modulated selected ion species isolation in a quadrupole ion trap

Abstract: A method of isolating selected ion species in a quadrupole ion trap mass spectrometer is disclosed. One or more ranges of masses to be eliminated from the ion trap are ejected by applying a supplemental dipole excitation waveform, sparsely populated with frequency components, while the trapping field is modulated. The spacing of the frequency components in the supplemental excitation waveform varies across the range of frequencies in the waveform. Preferably, the frequency range is divided into a plurality of subranges, and the spacing of the frequency components in each of the subranges is constant. A method of creating a master set of frequencies used for generating a supplemental excitation waveform is also shown. Likewise, a method of calculating edge frequencies defining a gap in the mass spectrum that is excited by the supplemental waveform is also shown. Modulation of the trapping field may be varied while the supplemental excitation waveform is applied to change the width of the gap in the mass spectrum.

Nmr sample cell

Abstract: The present invention relates to improving the sensitivity of an NMR system for electrically conductive (polar) NMR samples. Many NMR samples use water or a salt solution of water or other electrically conductive liquid as a solvent for biologically active materials. When such a sample is placed in the probe coil of an NMR spectrometer, electrical losses in the conductive material lowers the Q of the receiving circuit and thereby reduces the sensitivity of the spectrometer. These electrical losses can be greatly reduced by breaking up the current paths within the sample. This can be achieved by a special sample cell that compartmentalizes the sample with electrical insulating material reducing the electrical current paths.

Electrode designs for controlling uniformity profiles in plasma processing reactors

Abstract: Electrode designs for reducing the problem of non-uniform etch in large diameter substrates are presented. The electrode opposite the substrate being etched in a plasma reactor can be tailored as to its shape so as to control the uniformity of the etching across the substrate. This is achieved with a number of generally dome-shaped electrode structures including generally cone-shaped electrodes, generally pyramidally-shaped electrodes and generally hemispherically-shaped electrodes. It is believed that non-uniformity of etching is due, at least in part, to excess ion density at the center of the reactor. The dome-shaped electrodes serve to disperse the high concentration of ions from the center of the reactor out toward the periphery of the substrate and thereby even out the ion density distribution across the substrate being etched. The electrodes are useable in diode plasma reactors, triode plasma reactors and ICP plasma reactors.

Quadrupole trap ion isolation method

Abstract: A method for efficiently filling a QIT (1) which isolates an ion range by employing a sequential part of supplemental broadband waveforms where the first such supplemental broadband waveform is applied during the period that the e-beam ionization bombardment takes place and the second such broadband waveform is applied after the e-beam bombardment ends.

A 130-260 GHz, 1 MW free electron maser for fusion

Abstract: We report on design work and testing of several main components of the FOM-Fusion-FEM project. Measurements on the electron gun are presented, showing a uniform beam current profile and a low halo current. A time-dependent simulation study of the interaction between the electron beam and the mm-waves shows that, for proper undulator tapering, longitudinal mode competition results in a quasi single-mode regime. Further, some high power and detailed low power measurements on mock-ups of the waveguide system are presented, showing that the reflection and outcoupling systems perform well.

A method of selective ion trapping for quadrupole ion trap mass spectrometers

Abstract: A power efficient selective mass range trap filling process in which the RF trapping voltage (46) connected to the ring electrode (10) is slowly modulated simultaneously with: (1) e-beam ionization bombardment (41) and (2) application of a broadband supplemental waveform (49) containing selected secular frequencies to the QIT end caps (8, 9). The modulation (42) permits the reduction of the number of frequency components required in the broadband supplemental waveform (49) and permits elimination of absorption by ions of energy from more than one supplemental frequency component at any one time.

Modeling broad-area DBR/DFB lasers

Abstract: A variety of broad-area semiconductor laser devices are currently providing high-power with near diffraction-limited performance. These new devices share an important design element: the suppression of filamentation tendencies. Specific designs include traveling-wave amplifiers and reflective-wave amplifiers, tapered amplifiers, unstable resonator oscillators and most recently, curved or angled grating DBR/DFB oscillators. These latter designs offer the advantages of filament suppression and angular spectrum filtering, while providing strong spectral filtering as well. We review the motivation and design principles for several of the new broad-area DBR/DFB devices and describe the algorithms that have been developed in order to provide accurate numerical simulations and performance predictions.

Spectral modification through phase modulation with spatial extent

Abstract: An optical pulse propogating in an optical guide of an electro-optic medium interacts with a coplanar RF traveling wave to shift the optical wavelength. The RF phase is resynchronized to the optical pulse phase with spatial periodicity to provide a desired phase relationship between RF and optical radiation. A unidirectional incremental wavelength shifter comprises a frequency multiplexer for soliton communication and a symmetrical sideband modulator of this type varies the spectral width of probe illumination in an atomic absorption spectrometer probe beam.

Single field emission device

Abstract: A field emission device (100) uses single crystals in order to eliminate grain boundaries within some or all of the electrodes (103, 104, and 205). The elimination of grain boundaries reduces susceptibility to damage, improves stability of the device (100), and improves uniformity and reproducibility among devices. In a preferred embodiment, the emitter and gate electrodes (103 and 104 respectively) are formed from a single crystal thin film (302). In other embodiments, other structures are employed wherein one or more of the electrodes (103, 104, and 205) are formed from single crystals.

Step-edge and stacked-heterostructure high-T/sub c/ Josephson junctions for voltage-standard arrays

Abstract: We have explored two high-transition-temperature Josephson junction technologies for application in voltage standard arrays: step-edge junctions made with YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// and Au normal-metal bridges, and stacked series arrays of Josephson junctions in selectively doped, epitaxially grown Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ heterostructures. For both kinds of junctions, Shapiro steps induced by a microwave bias were characterized as a function of power. We compare the technologies with respect to critical current and normal resistance uniformity, maximum achievable critical current, critical-current normal-resistance product, and operating temperature. >

Surface coating to improve performance of ion trap mass spectrometers

Abstract: The interior surfaces of an ion trap or ionization chamber is coated with an inert, inorganic non-metallic insulator or semiconductor material for the passivation of such surfaces so as to minimize absorption, degradation or decomposition of a sample in contact with the surface.

Thin film heat treatment apparatus with conductively heated table and surrounding radiation shield

Abstract: The thin film heat treatment apparatus for heating the wafers or foil sheets provides a conductively heated table disposed within a vacuum chamber, a heat radiation preventing device that is installed adjacent to the conductively heated table and forms a space with the top of the heater table by surrounding the foil sheet or wafer placed on the top of the heater table.

Transport in atomically engineered BiSrCaCuO multilayers

Abstract: We have utilized atomic layer deposition to synthesize single crystal thin films of cuprate superconductors, as well as a variety of superlattices and multilayer heterostructures with atomically abrupt interfaces. For example, we made trilayer structures with the top and the bottom BiSrCaCuO electrodes separated by titanate barriers that were only 4 A thick and yet free of pinholes over macroscopic areas. This unique synthetic capability made it possible to study transport in thec-axis direction under controlled and systematically varied conditions. Taken together, these experiments provide a picture of thec-axis transport in 2201, 2212, and various heterostructures under study. In particular, they suggest presence of a large density of localized states near the Fermi level and thus support a two-component description of the electron system in these compounds.

Electron capture detector with guard electrode

Abstract: An improved ECD employing an ECD cell having a third electrode, i.e. guard positioned between the ECD cell field electrodes. The guard electrode is physically interposed between said field electrodes to divert all leakage current in the support insulators which flow between the field electrodes. The guard electrode ECD cell provides improved linear dynamic range as well as avoiding deterioration from handling during manufacture or repair.

Cuprate trilayer c-axis tunnelling heterostructures

Abstract: Trilayer tunneling structures consisting of cuprate electrodes and titanate barriers were grown by atomic layer-by-layer molecular beam epitaxy and processed into c-axis transport samples. Barriers of SrTiO/sub 3/ and related titanates with thicknesses ranging from 4 /spl Aring/ to 28 /spl Aring/ (one to seven unit cells of the titanate) were grown. While no supercurrent was observed for even the thinnest barrier, the zero bias resistance was an exponential function of barrier thickness for samples with five or fewer titanate unit cell barriers, indicating tunneling transport. Each additional titanate unit cell caused the zero bias resistance to increase by one order of magnitude. A detailed investigation of the properties of the cuprate layers immediately adjacent to the titanate layers revealed that they were depleted of charge carriers and exhibited variable range hopping transport. Thus the electron states in these layers were localized. The trilayer transport process is modeled as one phonon assisted tunneling between localized states. >