| 1. |
- Andersson, Henrik, 1975-, et al.
(författare)
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Analysis and improvement of the position nonlinearity caused by a residual stress in MOS-type position-sensitive detectors with indium tin oxide gate contact
- 2008
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 23:7, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, lateral effect position-sensitive detectors based on the MOS principle have been fabricated in lengths of 15 mm, 45 mm and 60 mm. The gate contact covering the active area consists of indium tin oxide which is a degenerate semiconductor transparent in the visible spectral range. Characterization and analysis have both been performed especially withparticular focus on the nonlinearity believed to be caused by stray stress induced in the inversion channel originating in the indium tin oxide gate contact. Stress in the channel will change the resistance in a non-uniform manner because of the piezoresistance effect, thus causing a nonlinearity in the position determination. It has been shown that the heat treatmentgreatly influences the linearity of the position-sensitive detectors. A heat treatment performed correctly results in 60 mm and 15 mm detectors with nonlinearity within ±0.1% and 45 mm detectors with nonlinearity within ±0.15% over 60% of the active length. This is an improvement over the previous results with this type of MOS position-sensitive detector. By performing a correctly timed heat treatment this PSD type has the potential to be used incommon position-sensing applications.
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| 2. |
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| 3. |
- Andersson, Henrik
(författare)
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Development of Process Technology for Photon Radiation Measurement Applications
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents work related to new types of photo detectors and their applications. The focus has been on the development of process technology and methods by means of experimentation and measurements. The overall aim has been to develop and improve photon radiation measurement applications which are possible to manufacture using standard Si processing technology. A new type of position sensitive detector that has switching possibilities based on the MOS principle has been fabricated and characterized. The influence of mechanical stress on the linearity of position sensitive detectors has been investigated. The results show that mechanical stress arising, for example, by the mounting of detectors in capsules can have an impact on device performance. Under normal circumstances these effects are rather small, but are considered to be worthwhile taking into account. Electroless deposition of Nickel including various dopants in porous silicon was performed to manufacture electrical contacts for this interesting material. After heat treatment it was confirmed by X-ray diffraction that Nickel silicide had been formed and I-V measurements show that different contacts exhibit Ohmic and rectifying behaviour. Spectrometers are used extensively in the process and food industry to measure both the chemical content and the amount of substances used during manufacturing. These instruments are often rather bulky and costly, though the trend is towards smaller and more portable equipment. A spectrometer based on an array of Fabry-Perot interferometers mounted close to an array detector is shown to be a viable option for the manufacture of a very compact device. Such a device has minimal intermediate optics and it may be possible, in the future, for it to be developed and completely integrated with a detector array into a single unit.
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| 4. |
- Andersson, Henrik, et al.
(författare)
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Electroless deposition and silicidation of Ni contacts into p-type Porous Silicon
- 2008
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Ingår i: Journal of porous materials. - : Springer Science and Business Media LLC. - 1380-2224 .- 1573-4854. ; 15:3, s. 335-341
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Tidskriftsartikel (refereegranskat)abstract
- Porous Silicon (PS) has attracted much attention since the discovery of its photo luminescent behavior. It has also been used for various other applications such as electroluminescent light emitting-diodes (LEDs), photodetectors and solar cells. For such devices, it is important to make good metallic Ohmic contacts to the PS in order to maximize the efficiency. In order to produce buried contacts, barrier layers, Schottky devices, etc. in PS, it is advantageous to deposit metal that covers not only the surface of the porous layer, but also the inside walls and the bottom of the pores. In this work experiments were performed to examine the morphology and properties of electroless deposition of Nickel into p-type PS and subsequent formation of Nickel silicide after heat treatment. Circular PS samples of 6 mm diameter were produced by anodizing p-type Silicon wafers for 15 min and were subsequently plated with Ni using three different plating baths. The pores are on average 20 µm deep and 4 µm wide. Two samples of each type were heat treated in an nitrogen atmosphere for one hour at 400 and 600°C respectively to produce Nickel silicide. Reference samples were made by means of electron beam evaporation of Ni. SEM micrographs show that the best pore coverage was achieved using the Ni plating bath containing hypophosphite. I–V characterization shows that different rectifying and Ohmic contacts can be formed between electroless deposited Ni and PS depending on the conditions of the heat treatment. XRD and EDX characterizations show that both the NiSi and Ni2Si phases exist in the sample at the same time.
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| 5. |
- Andersson, Henrik, et al.
(författare)
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Evaluation of an Integrated Fourier-Transform Spectrometer Utilizing a Lateral Effect Position Sensitive Detector with a Multi-Channel Fabry-Perot Interferometer
- 2008
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 19:4, s. 045306-
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Tidskriftsartikel (refereegranskat)abstract
- The basis of this paper is the evaluation of an integrated multi-channel Fourier-transform (FT) spectrometer based on a multi-channel wedge Fabry-Perot interferometer and a one-dimensional lateral effect position sensitive detector (PSD). The use of a PSD for an interferogram readout allows for a simple scanning mechanism with no requirement for any position reference. The use of a wedge-shaped interferometer makes it possible to integrate it directly onto the PSD surface, thus producing a very compact spectrometer. The capabilities of the spectrometer are demonstrated by absorption spectral measurements using a reference sample. In addition, spectral measurements on 532 nm DPSS and 632.8 nm He-Ne lasers are presented. The resolution of the spectrometer is approximately 5 nm. The evaluated spectrometer set-up can be used in applications where compact and low cost spectrometers are required, such as in process control and in education. Further, it is shown that there are deteriorations in very high accuracy position measurements, which are caused by changes in incident light intensity. A model describing the above-mentioned nonlinearities was developed based on analysing the equivalent circuit for PSDs and parameters such as leakage current and serial resistance. Additionally, a method is proposed to assist in the reduction of the nonlinearity caused by this effect.
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| 6. |
- Andersson, Henrik, 1975-
(författare)
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Position Sensitive Detectors : Device Technology and Applications in Spectroscopy
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the development, processing and characterization of position sensitive detectors and, in addition, to the development of compact and cost effective spectrometers. Position sensitive detectors are used to measure, with great accuracy and speed, the position of a light spot incident on the surface. Their main use is for triangulation, displacement and vibration measurements. A type of position sensitive detector based on the MOS principle and using optically transparent indium tin oxide as a gate contact has been developed. This type of detector utilizes the MOS principle where an induced channel forms beneath the gate oxide in the surface of the Silicon substrate. One and two dimensional detectors have both been fabricated and characterized. The first measurements showed that the linearity did not fulfil expectations and it was suspected that stress induced by the gate contact could be the reason for the seemingly high nonlinearity. Further investigations into both the p-n junction and the MOS type position sensitive detectors lead to the conclusion that the indium tin oxide gate is responsible for inducing a substantial stress in the surface of the detector, thus giving rise to increased position nonlinearity. The heat treatment step which was conducted was determined to be critical as either a too short or too long heat treatment resulted in stress in the gate and channel leading to position nonlinearity. If a correctly timed heat treatment is performed then the detector’s linearity is in parity with the best commercial position sensitive detectors. In addition, the development of very small, compact and cost effective spectrometers has been performed with the aim of constructing devices for use in the process industry. The development of a wedge shaped array of Fabry-Perot interferometers that can be mounted directly on top of a detector makes it possible to construct a very compact spectrometer using the minimum amount of optics. This wedge interferometer has been evaluated by means of array pixel detectors and position sensitive detectors for both the infrared and the visible wavelength ranges. When used with a position sensitive detector it is necessary to use a slit to record the intensity of the interferogram for many points over the detector, equivalent to pixels on an array detector. Usually the use of moving parts in a spectrometer will impose the use of high precision scanning mechanisms and calibration. By using a position sensitive detector for the interferogram readout both the position and the intensity are known for every measurement point and thus the demands placed on the scanning system are minimized.
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| 7. |
- Andersson, Henrik, et al.
(författare)
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Principle of FT Spectrometer based on a Lateral Effect Position Sensitive Detector and Multi Channel Fabry-Perot Interferometer
- 2009
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 42:5, s. 668-671
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Tidskriftsartikel (refereegranskat)abstract
- The principle of a new type of multi channel Fourier-Transform spectrometer based on a multi channel wedge Fabry-Perot interferometer using a one dimensional lateral effect Position Sensitive Detector and a scanning slit for interferogram readout have been shown. The design of this spectrometer is very compact and the readout electronics very simple. The drawback of using a scanning slit system is minimized by the use of a position sensitive detector where the position is inherently known for each measurement. Experiments show that the position can be resolved with high accuracy and the summation of the two photocurrents gives the interferogram after scanning the slit between the wedge interferometer and the position sensitive detector. The spectral resolution obtained with a 25mm wedge interferometer together with a 45mm position sensitive detector and a 25µm slit is about 5nm around 600nm wavelength range, which is close to the theoretically anticipated resolution. The evaluated spectrometer setup show promising results and could be used in applications where compact and low cost spectrometers are required.
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| 8. |
- Andersson, Henrik, et al.
(författare)
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Processing and Characterization of a MOS Type Tetra Lateral Position Sensitive Detector with Indium Tin Oxide Gate Contact
- 2008
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 8:9-10, s. 1704-1709
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Tidskriftsartikel (refereegranskat)abstract
- A 2-D tetra lateral position sensitive detector (PSD) based on the metal-oxide-semiconductor (MOS) principle has been manufactured and characterized. The active area of the device is 5 nun x 5 mm and the intention is to use the central 4 nun x 4 nun for low nonlinearity measurements. The gate contact is made of indium tin oxide (ITO) that is a degenerate electrically conducting semiconductor, which, in addition, is also transparent in the visible part of the spectrum. The use of a MOS structure results in a processing with no necessity to use implantation or diffusion in order to make the resistive p-layer as in a conventional p-n junction lateral effect PSD. Position measurements show good linearity in the middle 4 nun x 4 mm area. Within the middle 2.1 mm x 2.1 mm, the nonlinearity is within 1.7% of the active area with a position detection error of maximum 60 mu m. Measured MOS IV characteristics are compared to a level 3 spice model fit and show good agreement. The threshold voltage is determined to be -0.03 V. Responsivity measurements show a high sensitivity in the visible spectral region.
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| 9. |
- Andersson, Henrik, et al.
(författare)
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The effect of mechanical stress on lateral-effect position sensitive detector characteristics
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 563:1, s. 150-154
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Tidskriftsartikel (refereegranskat)abstract
- Position-sensitive detectors (PSDs) are widely used in noncontact measurement systems. In order to minimize the size of such systems, interest has increased in mounting the PSD chip directly onto printed circuit boards (PCBs). Stress may be induced in the PSD because of the large differences in thermal expansion coefficients, as well as the long-term geometrical stability of the chip packaging. Mechanical stress has previously been shown to have an effect on the performance of semiconductors. The accuracy, or linearity, of a lateral effect PSD is largely dependent on the homogeneity of the resistive layer. Variations of the resistivity over the active area of the PSD will result in an uneven distribution of photo-generated current, and hence an error in the readout position. In this work experiments were performed to investigate the influence of anisotropic mechanical stress in terms of nonlinearity. PSD chips of 60×3 mm active area were subjected, respectively, to different amounts of compressive and tensile stress to determine the influence on the linearity.
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| 10. |
- Esebamen, Omeime, et al.
(författare)
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Spectral Performance of Photon Counting Pixel Detector Using Attenuation Spectra for Test Samples
- 2009
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Ingår i: AIP Conference Proceedings Volume 1204. - New York : American Institute of Physics (AIP). - 9780735407411 ; , s. 177-179
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Konferensbidrag (refereegranskat)abstract
- When a material is placed along the path of an X-ray beam using a broad range of energy X-ray source, the energy dependence of the attenuation for the X-ray photons will be substantially dissimilar for different materials. The process at which X-ray radiation loses its penetrating strength as it travels through a material will be significantly larger for photons with energy above k-edge energy of that material than for those with slightly lower energy. Hence energy resolved X-ray imaging can be used to achieve colour images revealing the material content of the test sample. The attenuation of the spectrum done by scanning an energy window through the spectrum was measured for a number of samples of different materials. The test samples include Sn, Gd and I with K-edge energy at 29 keV, 50 keV and 33 keV, respectively, using a Feinfocus microfocus X-ray source (FTP-105.02) with Medipix2 photon counting chip.
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