H. Olin - Academia.edu (original) (raw)

Papers by H. Olin

Scientific reports, Jan 28, 2018

The triboelectric effect, charging by contact, is the working principle in a device called a trib... more The triboelectric effect, charging by contact, is the working principle in a device called a triboelectric nanogenerator. They are used as efficient energy transducers in energy harvesting. In such generators the charging of surfaces at contact is followed by a separation of the surfaces increasing the electrical energy which can subsequently be used. Different materials have different triboelectric potentials leading to charging at contact. The temperature dependence of the charging has just recently been studied: the triboelectric effect is decreasing with temperature for a generator of Al-PTFE-Cu. Here, we suggest a mechanism to explain this effect assuming ion transfer using a two-level Schottky model where the two levels corresponds to the two surfaces. The difference in binding energy for ions on the two surfaces then enters the formula for charging. We fit the triboelectric power density as a function of temperature obtained from a two-level Schottky model to measured data fo...

An ex situ process has been developed to produce thin superconducting T12Ba2CaCu208 films. The pr... more An ex situ process has been developed to produce thin superconducting T12Ba2CaCu208 films. The properties of films grown on different substrates using different annealing regimes were studied. Critical temperatures of 103-107 K were measured on films prepared in a broad range of annealing temperatures on SrTiO3, LaAIO3, and Y-ZrQ substrates. A critical current density, Jc, of 2 x 106 A/cm 2 at 77 K was measured on LaA103. Film morphology was studied by SEM, AFM, and STM.

Physical Review B, 1997

In situ Na intercalation of the layered compound VSe 2 has been studied with photoemission and sc... more In situ Na intercalation of the layered compound VSe 2 has been studied with photoemission and scanning tunneling microscopy. Core-level spectroscopy proves that Na deposited in UHV onto the VSe 2 surface rapidly intercalates, leaving only small amounts at the surface. The scanning tunneling microscopy measurements show that the intercalated Na is not uniformly distributed between the VSe 2 layers, but preferentially in two-dimensional islands. Thus the surface region is divided into intercalated and nonintercalated areas. Holelike features in the intercalated areas are interpreted as locally missing Na. ͓S0163-1829͑97͒01415-X͔

Physical review. B, Condensed matter, Jan 15, 1995

We have studied the atomic and electronic structures of 4Hb-TaS 2 , which has alternating layers ... more We have studied the atomic and electronic structures of 4Hb-TaS 2 , which has alternating layers of the 1T and 1H type, at room temperature and 77 K, using a scanning tunneling microscope. Using a layer-by-layer etching technique, we fabricated staircases with alternating layers of the 1T and 1H type. The T-type layers showed the typical ͱ13ϫͱ13 charge-density-wave structures, whereas the H-type layers had the triangular atomic structure at both temperatures. The measured tunneling spectra of each layer at 77 K showed entirely different characteristics; the 1H layer remained in the metallic state, whereas the 1T layer showed an insulating behavior with a wide opening of the energy gap at the Fermi level at 77 K.

Journal of the Less Common Metals, 1990

Abstract YBCO thin films were fabricated by laser deposition, in situ on MgO substrates, using bo... more Abstract YBCO thin films were fabricated by laser deposition, in situ on MgO substrates, using both O 2 and N 2 O as process gas. Films with T c above 90 K and jc of 10 6 A/cm 2 at 77 K were grown in oxygen at a substrate temperature of 765 C. Using N 2 O, the optimum substrate temperature was 745 C, giving a T c of 87 K. At lower temperatures, the films made in N 2 O had higher T c (79 K) than the films made in oxygen (66 K). SEM and STM investigations of the film surfaces showed the films to consist of a comparatively smooth ...

Dye-sensitized solar cell (DSSC) is a low cost and efficient way to transform solar radiation to ... more Dye-sensitized solar cell (DSSC) is a low cost and efficient way to transform solar radiation to electricity. Indium tin oxide (ITO) and fluorine doped tin oxide (FTO) coated glass are two kinds of transparent electrodes that are mostly used to fabricate DSSCs. However, these two kinds electrodes lack flexibility, limiting their development. [1] Flexible electrodes are desired in DSSC because of they are lightweight, low cost and ro田l-to-roll compatible. There are attempts to replace both [1] or one [2] of the two electrodes in DSSC. However, the efficiencies are relatively low. Here we reported a simple method to fabricate graphite-carbon nanotube (G-CNT) composited flexible electrode for using as counter electrode in DSSC. The electrodes are simple fabricated by reverse filtration and flash sintering, leading to highly flexible (360 °C) and conductive (sheet resistance, 100 Ohm/sq) electrodes that can be used as both catalyzer and current collector. The energy conversion efficiency of such electrode based DSSC can reach 2.02% with fill factor of 0.56 (Figure 1). Figure 1. Photograph of the G-CNT composited flexible electrode, and the J-V characterization of the fabricated DSSC. References: [1] W. Wang, Q. Zhang, H. Li, G. W. Wu, D. C. Zou, D. P. Yu, Adv. Funct. Mater. 2012, 22, 2775-2782.[2] B. Wang, L. L. Kerr, Sol. Energy Mater. Sol. Cells. 2011, 95, 2531-2535.

Nanoscale Science and Technology, 1998

Abstract. When two metal electrodes are separated, a nanometer sized wire (nanowire) is formed ju... more Abstract. When two metal electrodes are separated, a nanometer sized wire (nanowire) is formed just before the contact breaks. The electrical conduction measured during this retraction process shows signs of quantized conductance in units of GO= 2e2/h. Recent experiments show that the force acting on the wire during separation fluctuate, which is interpreted as due to atomic rearrangements. In this report we use a simple free electron model and show that the electronic contribution to the force fluctuations are comparable to ...

We briefly present a method for the parameterization of assembly systems derived from their abili... more We briefly present a method for the parameterization of assembly systems derived from their ability to form unique structures. The concept of bond uniqueness is introduced and we show how it influences the number of unique structures that a programmable, or algorithmic, self-assembly system can create. Further, we argue that programmable self-assembly systems create embedded, additional computation that is reflected

Ultramicroscopy, 1992

Using an STM in air, we have studied three different electropolished Ti surfaces. One sample was ... more Using an STM in air, we have studied three different electropolished Ti surfaces. One sample was analyzed without further treatment. The second was thermally oxidized in air at 500°C. The third was exposed to an argon glow discharge and then oxidized in pure oxygen. The samples were characterized by Auger spectroscopy prior to STM measurements. Electropolished and thermally oxidized samples showed a granular structure, with a low corrugation between 2 and 10 nm. At a larger scale, the glow discharge treated sample showed a high corrugation ~ 100 nm.

Review of Scientific Instruments, 2003

Physica C: Superconductivity, 1994

Patterns were defined on SrTiO3 substrates by means of photolithography and trenches were etched ... more Patterns were defined on SrTiO3 substrates by means of photolithography and trenches were etched in the substrate by ion beam milling. By heating the resist to 170 °C, a rounded resist profile was obtained. When milling the rotating samples at an incidence angle of 30 ° from the surface plane this gave a slope angle of the trench walls of <35 °. YBa2Cu30 7 thin films were deposited on the patterned substrates and the structure was planarized by mechanical polishing. The obtained surface had a uniform morphology, as investigated with AFM, and all outgrowths and pinholes of the YBCO film were removed. These structures should be useful for crossover preparation.

Physica B: Condensed Matter, 1994

Abstract We have used a dilution refrigerator cooled STM for investigating the vortex state in le... more Abstract We have used a dilution refrigerator cooled STM for investigating the vortex state in lead-bismuth alloy 4000Afilms. The vortices were recognized by the decreasing dynamic conductance near the gap voltage when the instrument was operated in its normal feed back mode. A clean surface suitable for tunneling was maintained by a 75Alayer of gold deposited on top of the sample film. The temperature was kept at 80 mK and magnetic fields between 0 and 0.2 T were used.

Microscopy and Microanalysis, 2005

As one tries to diminish the size of electrical circuits there is a problem with increasing elect... more As one tries to diminish the size of electrical circuits there is a problem with increasing electrical current densities. Regular wires can withstand current densities of up to approximately 10 4 A/cm 2 where resistive heating becomes a problem and can cause electrical failure. This can be circumvented by using thin metal film conductors on heat sinks, and current densities of up about 10 7 A/cm 2 can then be sustained. At even higher current densities another problem appears; electromigration. Strong electrical fields and high electron currents will cause material to migrate and result in circuit failures. A possible solution to this problem could be the use of carbon nanotubes as these may display ballistic conduction and be able to withstand very high current densities. Detailed studies of electromigration are not easy, as they require imaging with high spatial resolution and an ability to locally apply strong electrical fields and currents.

Measurement Science and Technology, 1997

A compact, less than 0.3 cm 3 , scanning tunnelling microscope (STM) based on a new inertial slid... more A compact, less than 0.3 cm 3 , scanning tunnelling microscope (STM) based on a new inertial slider design is presented. The STM is built of two concentric piezoelectric tubes, the inner one for scanning the tip and the outer one for inertial sliding of the sample to and from the tip. The coarse approach is made by inertial sliding of the sample along a plane that is non-perpendicular to the tip, while the sample surface is kept perpendicular to the tip throughout inertial sliding and image acquisitions. The compact design ensures a mechanical noise level of less than 0.1Å.

Measurement Science and Technology, 1994

A compact scanning probe microscope for operation in air and liquid is described. The probe techn... more A compact scanning probe microscope for operation in air and liquid is described. The probe techniques implemented are scanning tunnelling microscopy and scanning ion conductance microscopy. The software, electronics, mechanical construction and some representative measurements will be presented here. The compact and concentric microscope head is built around a commercial piezoelectric inchworm motor. The scanner is a standard piezo tube. An analogue feedback system is used lor taking images, while digitai controi of the probe-sample distance is used for other experiments, such as measurements of current-voitage characteristics. A Macintosh personal computer is used for controi and presentation of data. A simple method to make scanning tunnelling microscope tips suitable for electrochemical use is described. The microscope has a high resonance frequency (9.6 kHz), low noise (0.01 nm Hz-'i 2 at 10 Hz), low thermal drift (less than 0.1 nm mln-'), and high acoustical noise suppression. The current-distance-dependency of the scanning ion conductance microscope was found to be linear.

Journal of the American Chemical Society, 2003

We report a "clean" and fast process, utilizing supercritical carbon dioxide, for producing ultra... more We report a "clean" and fast process, utilizing supercritical carbon dioxide, for producing ultrahigh densities, up to 10 12 nanowires per square centimeter, of ordered germanium nanowires on silicon and quartz substrates. Uniform mesoporous thin films were employed as templates for the nucleation and growth of unidirectional nanowire arrays orientated almost perpendicular to a substrate surface. Additionally, these nanocomposite materials display room-temperature photoluminescence (PL), the energy of which is dependent on the diameter of the encased nanowires. The ability to synthesis ultrahigh-density arrays of semiconducting nanowires on-chip is a key step in future "bottom-up" fabrication of multilayered device architectures for nanoelectronic and optoelectronic devices.

Journal of Superconductivity, 1994

Anex situ process has been developed to produce thin superconducting Tl 2 Ba 2 CaCu 2 O 8 films. ... more Anex situ process has been developed to produce thin superconducting Tl 2 Ba 2 CaCu 2 O 8 films. The properties of films grown on different substrates using different annealing regimes were studied. Critical temperatures of 103–107 K were measured on films prepared in a broad range of annealing temperatures on SrTiO 3, LaAlO 3, and Y-ZrO 2 substrates. A critical current density, J c, of 2× 10 6 A/cm 2 at 77 K was measured on LaAlO 3. Film morphology was studied by SEM, AFM, and STM.

Journal of Microscopy, 2003

We present a method for combined far-field Raman imaging, topography analysis and near-field spec... more We present a method for combined far-field Raman imaging, topography analysis and near-field spectroscopy. Surfaceenhanced Raman spectra of Rhodamine 6G (R6G) deposited on silver nanoparticles were recorded using a bent fibre aperture-type near-field scanning optical microscope (NSOM) operated in illumination mode. Special measures were taken to enable optical normal-force detection for control of the tip-sample distance. Comparisons between far-field Raman images of R6G-covered Ag particle aggregates with topographic images recorded using atomic force microscopy (AFM) indicate saturation effects due to resonance excitation.

Journal of Colloid and Interface Science, 2010

A single-step, premixing method was used to directly deposit gold nanoparticles on Mo 6 S 3 I 6 (... more A single-step, premixing method was used to directly deposit gold nanoparticles on Mo 6 S 3 I 6 (MSI) molecular wire bundles. Gold nanoparticles with different sizes and densities were coated on the MSI by changing the concentration of the gold containing salt, HAuCl 4. TEM, SEM, and EDX characterization showed deposition of gold nanoparticles on the MSI nanowire surface. The electrical resistance of these MSI-Au composites was more than 100 times lower than that for pure MSI, and was mainly dependent on the density of the deposited gold nanoparticles. Furthermore, we immobilized thiol group-labeled oligonucleotide on the composites and then hybridized with a fully matched sequence. The resistance of the MSI-Au composites increased during the thiol step, while it decreased by hybridizing, due to the conductance difference between single-and double-stranded DNA chains. These results indicate that this new kind of MSI-Au composite could be used as a platform for different applications, including biosensors.

IEEE Transactions on Appiled Superconductivity, 1995