| 1. |
- ANDERSEN, JN, et al.
(författare)
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SURFACE RELATED CORE LEVEL SHIFTS FOR THE SI(111)SQUARE-ROOT-3X SQUARE-ROOT-3 - AL SYSTEM
- 1991
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 9:4, s. 2384-2387
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Tidskriftsartikel (refereegranskat)abstract
- The Si(111) square-root 3 x square-root 3:Al reconstruction has been studied by surface sensitive high resolution core level spectroscopy. It is shown that three components are needed to fit the Si 2p spectra. The Al2p emission is found to consist of more than one component and it is argued that this is related to defects in the overlayer.
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| 2. |
- Bilenberg, B, et al.
(författare)
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Topas-based lab-on-a-chip microsystems fabricated by thermal nanoimprint lithography
- 2005
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Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 23:6, s. 2944-2949
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Tidskriftsartikel (refereegranskat)abstract
- We, present a one-step technology for fabrication of Topas-based lab-on-a-chip (LOC) microsysterris by the use of thermal nanoimprint lithography (NIL). The technology is demonstrated by the fabrication of two working devices: a particle separator and a LOC with integrated optics for absorbance measurements. These applications demonstrate the fabrication of millimeter to micrometer-sized structures in one lithographic step. The use of NIL makes the technology easily scalable into the nanometer regime by the use of a suitable lithographic technique in the fabrication of the stamp. Processing issues such as environmental stress cracking of the Topas and the requirements to anti-sticking layers on the stamp when imprinting into Topas are discussed.
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| 3. |
- Bogdanov, A. L., et al.
(författare)
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Fabrication of arrays of nanometer size test structures for scanning probe microscope tips characterization
- 1994
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Ingår i: Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena. - : American Vacuum Society. - 0734-211X. ; 12:6, s. 3681-3684
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Konferensbidrag (refereegranskat)abstract
- A problem in scanning probe microscopy (SPM) is the unknown shape of the probing tip. Generally, the image is a convolution between the shape of the tip and the surface. Information of the shape of the probe may be gained by imaging very sharp tips. Here we present a method for making two-dimensional arrays of very sharp tips. The tip arrays were made of silicon using electron beam lithography with subsequent ion-beam etching. To achieve the best possible resolution, ultrasonic excitation was used during development of the bilayered PMMA resist. Thus, openings in the resist with size nearly equal to the spot size of the writing e-beam have been obtained. A further decrease of the radius of the tips was obtained by the choice of appropriate thickness for the masking NiCr layer. The tips were conical with a height up to 100 nm with a radius of the tip down to 10 nm. The tips were suitable for study of the shape of AFM probe tips, under condition that the tip array samples were rinsed in water prior to the measurement. Without the rinsing procedure, strong sticking forces between the probe and the sample would have eroded both of them. The regularity of the array provided an easy way to calibrate the lateral motion of the scanner
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| 4. |
- Boscarino, Diego, et al.
(författare)
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Deposition of silica-silver nanocomposites by magnetron cosputtering
- 2005
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:1, s. 11-19
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Tidskriftsartikel (refereegranskat)abstract
- Thin films have been grown on silicon and silica substrates by cosputtering of silica and silver in Ar, Ar+2.5% O2, and Ar+5% O2 gas mixtures. Rutherford backscattering spectrometry showed that the films have Ag atomic fractions xAg in the range of ∼1 to ∼10 at. %, and, by valence considerations, that the fraction of oxidized Ag in the films deposited in presence of oxygen is limited. Transmission electron microscopy images revealed the presence of Ag nanoclusters, with a mean size diameter not larger than 5 nm. The clusters are preferentially arranged along columns. It is suggested that the columns are regions with diameter in the nanometer range in which the density of the dielectric matrix is lower, thus favoring the formation of metal clusters. In presence of O2, the clusters were observed to have a more regular spherical shape. The optical absorption spectra of films grown in presence of O2 are distinguished from those grown in Ar by specific features, which are attributed to oxidation at the cluster surface. © 2005 American Vacuum Society.
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| 5. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Optical study of spin injection dynamics in InGaN/GaN quantum wells with GaMnN injection layers
- 2004
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 22:6, s. 2668-2672
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Tidskriftsartikel (refereegranskat)abstract
- The spin injection dynamics of GaMnN/InGaN multiquantum well (MQW) light emitting diodes (LEDs) grown by molecular beam epitaxy were examined using picosecond-transient and circularly polarized photoluminescence (PL) measurements. Even with the presence of a room temperature ferromagnetic GaMnN spin injector, the LEDs are shown to exhibit very low efficiency of spin injection. Based on resonant optical orientation spectroscopy, the spin loss in the structures is shown to be largely due to fast spin relaxation within the InGaN MQW, which itself destroys any spin polarization generated by optical spin orientation or electrical spin injection. Typical photoluminescence decay times were 20-40 ns in both commercial GaN MQW LEDs with emission wavelengths between 420-470 nm and in the GaMnN/InGaN multi-quantum well MQW LEDs. In the wurtzite InGaN/GaN system, biaxial strain at the interfaces give rise to large piezoelectric fields directed along the growth axis. This built-in piezofield breaks the reflection symmetry of confining potential leading to the presence of a large Rashba term in the conduction band Hamiltonian which is responsible for the short spin relaxation times.
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| 6. |
- Carlstrom, C. F., et al.
(författare)
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Characterization of damage in InP dry etched using nitrogen containing chemistries
- 2001
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 19:5, s. 1905-1910
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Tidskriftsartikel (refereegranskat)abstract
- Etching of InP by different ion beam etching processes using chemistries containing nitrogen, such as nitrogen milling, N(CH3)(3) and Ar/N(CH3)(3) based reactive ion beam etching (RIBS), and N-2/CH4/H-2 based chemically assisted ion beam etching (CAIBE), is investigated. The residual surface damage is characterized using I-V characteristics of Au/InP metal-semiconductor (MS) contacts and photoluminescence (PL) yield measurements from near surface quantum wells and bulls InP. The contacts formed on as-etched surfaces, irrespective of the etch process, show ohmic behavior. On the other hand, although the PL yield is reduced for the different processes, the measured intensities show variations which are attributed to passivation of defects by hydrogen. Secondary ion mass spectroscopy (SIMS) was used to check (qualitatively) the presence of nitrogen in the etched and annealed InP samples. SIMS data show the presence of nitrogen in the near surface region of the etched samples, but nitrogen levels drop to background levels upon annealing at typical regrowth conditions (650 degreesC under phosphine flow). Interestingly, the annealing step results not only in a significant recovery of the PL yield, but also in a recovery of Schottky characteristics of the Au contacts formed on the annealed surfaces. These observations show that the etch-induced damage is significantly reduced by annealing and suggests recovery of the near-surface stoichiometry and possibly reduction of nitrogen-related defects.
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| 7. |
- Douheret, O., et al.
(författare)
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Determination of spatial resolution in atomic-force-microscopy-based electrical characterization techniques using quantum well structures
- 2005
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:1, s. 61-65
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a procedure to determine the spatial resolution in scan ning capacitance (SCM) and scanning spreading resistance microscopy (SSRM) is proposed and demonstrated. It is based on profiling of confined carriers (in cross section) in quantum well (QW) structures consisting of QWs with different well widths and interwell spacing. Spatial resolution of sub-5 nm was observed for SSRM with commercially available diamond-coated silicon probes and sub-30 nm for SCM with IrPt5-coated probes. The influence of experimental parameters such as tip-sample bias and tip averaging on lateral resolution is discussed and appropriate measurement conditions for performing high-resolution measurements are highlighted. Finally, it is proposed that such structures can be used not only to select probes appropriate for high resolution measurements, but also in the development of new probes.
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| 8. |
- Eklund, Per, et al.
(författare)
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Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
- 2005
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:6, s. 2486-2495
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Tidskriftsartikel (refereegranskat)abstract
- We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300 °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290 GPa, respectively. The electrical resistivity was 330 µ cm for optimal Ar pressure (4 mTorr) and substrate temperature (300 °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6 µ at a contact force of 800 N compared to 3.2 µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.
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| 9. |
- Erlandsson, Ragnar, et al.
(författare)
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Gas-induced restructuring of palladium model catalysts studied with atomic force microscopy
- 1991
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 9:2, s. 825-828
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Tidskriftsartikel (refereegranskat)abstract
- The structure of thin Pd films evaporated onto planar SiO2 substrates changes dramatically during oxygen/hydrogen exposures in ultrahigh vacuum. In this work we have used an atomic force microscope(AFM), operated in the attractive mode, to obtain the three‐dimensional morphology of the Pd surface for different film thicknesses and treatments, and compared the data with transmission electron microscopy(TEM) micrographs. During restructuring, a 100‐Å film changes from being a smooth continuous film with cracks into metal clusters dispersed on the SiO2 support. In the 5‐Å case the metal films are already well dispersed as fabricated. Here the gas exposure instead results in a clustering effect resulting in larger particles. The AFM gives results which are consistent with TEM micrographs but also gives additional information on metal particle shape which can lead to a further understanding of the restructuring process.
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| 10. |
- Hedlund, Christer, 1964-, et al.
(författare)
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A Method for the Determination of the Angular Dependence during Dry Etching
- 1996
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 14:5, s. 3239-
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Tidskriftsartikel (refereegranskat)abstract
- Process simulation is going to play an ever increasing role in the development, process optimization, and production of integrated circuit devices, yielding shorter development times and reduced costs as compared to traditional development methods. One of the most notorious problems one faces in topography simulations in particular is the determination of the erosion/growth rates of materials exposed to a variety of complex physicochemical processes. The latter evolve continually to satisfy the needs of the ever advancing microelectronic industry, while our understanding about these processes is often incomplete and insufficient for their description. Existing theoreticalmodels, which are often semiempirical, include a set of fitting parameters which are generally unknown and their determination in most cases involves guesswork. Another much more pragmatical approach to the problem is to measure these etch/growth rates directly in situ in the production equipment and feed the data into a topography simulator. In this article we present a simple and general method for measuring the angular dependence of the etch rate of a variety of materials using specially patterned silicon wafers. With anisotropic wet etching of silicon wafers it is possible to create structures defined by specific crystallographic planes, thus producing a variety of planar orientations on one and the same wafer. The structures can be oxidized and coated with the material of interest and processed under standard operating conditions. The method will be presented together with angular dependence data from typical dry etching processes. The results will be used as an input to the topographysimulation program DINESE.
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