Pelle Rangsten

Diamond replicas from microstructured silicon masters

Abstract We are developing a microstructure technology for thick film diamond replicas, using deposition by hot filament chemical vapour deposition (CVD) on microstructured silicon. This technology is primarily intended to make micromechanical structures for microstructured carriers, fluidic cooling systems, systems for biochemical analyses and processes, and moulds for thermoplastic and metal microstructures. With thick film deposition ridges, trenches, and capillary channels with high resolution coverage and low roughness, rms

Field emitting structures intended for a miniature x-ray source

The concept of a miniature X-ray source is presented. The source consists of a micromachined field-emitting cathode and an anode. Electrons emitted from the cathode are accelerated towards and into the anode where their deceleration produces X-rays. The energy of the X-rays is controlled by the voltage applied to the electrodes, and the dose rate by the emission current. A tentative medical application is discussed and candidate field emission structures are investigated. Spectra from different anode materials have been collected using diamond cold cathodes.

Electrostatically excited diaphragm driven as a loudspeaker

Abstract This paper is focused on a hermetically sealed cavity which can be electrostatically excited and driven as a loudspeaker. The actuation principle is based on a diaphragm that is rolling against the cavity bottom to reach both large displacements and strong electrostatic forces. The loudspeaker is primarly intended for airborne ultrasound. Test speakers have been manufactured by micromachining in silicon using anisotropic and isotropic etching, and wafer bonding. Experiment shows an acoustic output of 112 dB in sound pressure level at the resonance frequency of 127 kHz, measured at a distance of 10 mm with 50 V peak-to-peak in applied driving voltage. An empirical Q -value of 7 is found. Measurements indicate that the resonance frequency of the loudspeaker can be tuned with an applied biasing voltage.

Etch rates of crystallographic planes in Z -cut quartz—experiments and simulation

The anisotropic etching behaviour of monocrystalline quartz is studied both experimentally and with computer simulations. The etch rate minima were identified as the crystal planes m, r, r(2), s an ...

Diamond microstructures for optical micro electromechanical systems

We have used hot filament chemical vapour deposition (HFCVD) to fabricate diamond microstructure components for optical micro electromechanical systems (MEMS). In order to demonstrate the wide application range for diamond technology we have made componen

Demonstration of a single use microsystem valve for high gas pressure applications

Demonstrated and characterized here is a single use valve developed for high-pressure applications. Incorporated within the single use valve is a particle filter. The filter serves to remove any particle debris created by the activation process. The valve is solder sealed to be leakage proof. The solder is remelted to obtain activation of the valve. Local heater elements are incorporated on the valve surface together with solder wetting pads. The gas mass flow through the device was evaluated prior to sealing and after activation. The valve was functional at pressures of 100 bar, and opened in less than 10 s with an applied power of 13 W.

Diamond Membrane Based Structures for Miniature X-ray Sources

Diamond membrane based structures for a miniature X-ray source are presented. The source consists of two microstructured diamond membranes, which are transparent to the generated radiation. One membrane works as a field emitting cathode and the other is covered with an anode thin film metal. A high voltage is applied between the electrodes and electrons emitted from the cathode are accelerated towards the anode metal where they produce X-rays. 15 kV X-ray spectra were collected through both membranes. The spatial distribution of the emitted bremsstrahlung and the characteristic radiation was investigated.

Quartz‐to‐Quartz Direct Bonding

Direct bonding of single crystalline quartz wafers is presented. By this straightforward technique, hermetical seals between quartz wafers can be formed. Nearly Z-cut (the Z-cut rotated 1 degrees 5 ...

Designed abrasive diamond surfaces

With the aim to explore their abrasive and grinding properties, flat diamond surfaces with protruding pyramidal abrasive tips have been designed and manufactured. The manufacturing process is a replica technique based on hot filament chemical vapour deposition of diamond onto a silicon wafer, in which the shape, size and packing pattern of the pyramids have been defined by photolithography and etching. After the diamond deposition, the silicon master is removed by etching and the thin diamond film is cemented to a supporting steel disk. Three different pyramid sizes, each with two different packing densities, were fabricated on the same silicon wafer. One of these structures was selected for further evaluation. The resulting shape and quality of the diamond surface was evaluated by scanning electron microscopy (SEM) and Raman spectroscopy. The abrasive properties and durability were evaluated in a pin-on-disc test followed by SEM studies of the abrasive structures and the abraded surfaces. The manufacturing process proved successful in producing well-defined abrasive diamond structures, showing practically constant tip shape and size. The diamond structures suffered negligible damage when abrading brass and tin, exhibited limited fracture when abrading steel, and rather extensive fracture when abrading aluminium oxide. The fracture was mainly due to an unintentional limited diamond thickness in the outermost parts of the pyramids. The combination of extreme mechanical properties of diamond and possibilities to design exceptionally well-defined abrasive structures promise very interesting possibilities for development of novel grinding tools and standardised abrasive wear tests.

Diamond microstructure replicas from silicon masters

We are developing a microstructure technology for thick film diamond replicas, using deposition by hot filament CVD on microstructured silicon. This technology is primarily intended to make micromechanical structures for building-sets, fluidic cooling systems, systems for biochemical analyses and processes, and moulds for thermoplastic microstructures. In the thick film deposition on trenches in silicon, complete filling was possible with an aspect ratio up to 1.6. At higher aspect ratios, voids or channels are formed within the diamond replica. Ridges, trenches and capillary channels with high resolution coverage and low roughness, rms<2 nm, were created. Demonstrator structures for microfluidic, building-sets and polymer moulding applications are presented.