Fluorescerende organiske forbindelser som tracere for boreslam ved boring av letebrønner

I denne oppgaven er noen fluorescerende fargestoffer blitt undersøkt som mulige tracerkandidater for sporing av borevæske under kjernetaking i forbindelse med boring av letebrønner for olje. Acridine orange, fluorescein, rhodamin B, rhodamin WT samt 13 forskjellige sulfonsyrer er vurdert. Av disse var det fluorescein som hadde flest ønskede egenskaper. Tracerkandidatene, med unntak av acridine orange og naftalensulfonsyrene, hadde en viss sorpsjon på leirer. Fluorescensen til tracerkandidatene ble borte eller betydelig svekket ved tilsetting av flere typer borevæsker, men ved å øke tracerkonsentrasjonene var det mulig å detektere fluorescein, acridine orange og noen av sulfonsyrene i flere av prøvene med boreslam. Emisjonsspekterene til de forskjellige kandidatene ble vurdert, og rhodaminforbindelsene hadde de mest egnete spekterene i forhold til bakgrunnsspektrene til sandstein, borevæsker og deres komponenter. Acridine orange har en bred emisjonstopp som gjør at det kan bli noe vanskelig å kvantifisere den. Sulfonsyrene har varierende spektra, men felles for dem alle er at det må en noe høyere konsenmtrasjon til for å tilsvarende fluorescensutbytte som de andre kandidatene. Fluorescein har, i likhet med rhodamineforbindelsene, en klart definert emisjonstopp, men ofte vil vil denne ligge i området med mye fluorescens fra bakgrunnen. Dersom fluoresceinkonsentrasjonen økes noe, vil dette problemet bli mindre eller forsvinne. Rhodamin WT og fluorescein ble på bakgrunn av de ovenfornevnte egenskapene sammen med litteraturstudier valg ut til flømningsforsøk. I flømningsforsøkene viste begge kandidatene at de fulgte vannet gjennom en sandsteinsplugg. Rhodamin WT var en tanke forsinket, men fulgte ellers vannets bevegelser

Minority carrier lifetimes in Cz-Si wafers with intentional V-I transitions

publishedVersio

Capillary forces as a limiting factor for sawing of ultrathin silicon wafers by diamond multi-wire saw

Succeeding with ultrathin silicon wafer sawing by diamond multi-wire saw, is not only a matter of optimization; the challenges of thin wafer production and the capability limit have not yet been fully understood. In this work, we have seen that regular pairing of wires occurs when the wire-wire separation distance is reduced below some critical value. The wire pairing leads to wire jumps on the wire guide rolls, and if the run is not stopped, it leads to wire breakage. Moreover, it effectively obstructs the production of wafers thinner than the critical wire-wire distance. We suggest that the physical explanation to the observed limitations to ultrathin wafer sawing, by diamond multi-wire saw, is related to the capillary force acting on the wires due to the sawing liquid bridge connecting the wires. The hypothesis is supported by simplified mathematical modelling including capillary and spring forces between infinitely long, parallel wires. The calculations suggest that capillary forces are the main reason for wire pairing, and that wire pairing will occur when the wire distance is below some critical distance. This matches the observed, experimental behavior. The critical distance will vary with wafer saw design and operation. To succeed with cutting very thin wafers, we recommend using lower surface tension sawing fluid or even dry in-cut, to reduce the capillary forces and thus decrease the critical wire separation distance, and to reduce wire oscillations to decrease the probability of sub-critical wire-wire separation distance. To reduce the vibration amplitude, shorter distance between the wire guide rolls, thinner wires, and increased wire tension are suggested.publishedVersio

Investigation of the Grain Boundary Character and Dislocation Density of Different Types of High Performance Multicrystalline Silicon

Wafers from three heights and two different lateral positions (corner and centre) of four industrial multicrystalline silicon ingots were analysed with respect to their grain structure and dislocation density. Three of the ingots were non-seeded and one ingot was seeded. It was found that there is a strong correlation between the ratio of the densities of (coincidence site lattice) CSL grain boundaries and high angle grain boundaries in the bottom of a block and the dislocation cluster density higher in the block. In general, the seeded blocks, both the corner and centre block, have a lower dislocation cluster density than in the non-seeded blocks, which displayed a large variation. The density of the random angle boundaries in the corner blocks of the non-seeded ingots was similar to the density in the seeded ingots, while the density in the centre blocks was lower. However, the density of CSL boundaries was higher in all the non-seeded than in the seeded ingots. It appears that both of these grain boundary densities influence the presence of dislocation clusters, and we propose they act as dislocation sinks and sources, respectively. The ability to generate small grain size material without seeding appears to be correlated to the morphology of the coating, which is generally rougher in the corner positions than in the middle. Furthermore, the density of twins and CSL boundaries depends on the growth mode during initial growth and thus on the degree of supercooling. Controlling both these properties is important in order to be able to successfully produce uniform quality high-performance multicrystalline silicon by the advantageous non-seeding method

Minority carrier lifetimes in Cz-Si wafers with intentional V-I transitions

A p-type Cz-Si crystal has been pulled with varying pulling speed in order to produce wafers containing two distinct regions; A region with silicon self-interstitial defects, and a vacancy dominated region. Band-to-band photoluminescence imaging has been used to study the minority charge carrier lifetimes in these wafers after different processing steps. Despite the different defects found in the different regions of the wafers carrier lifetimes appear to be uniform across the entire wafers, both for ungettered and gettered samples. Only after an oxidation process at 1100 °C oxygen related ring patterns become visible. It is, however, difficult to identify the band structure of the transition area between the regions among all the striations in the crystal

Capillary forces as a limiting factor for sawing of ultrathin silicon wafers by diamond multi-wire saw

Succeeding with ultrathin silicon wafer sawing by diamond multi-wire saw, is not only a matter of optimization; the challenges of thin wafer production and the capability limit have not yet been fully understood. In this work, we have seen that regular pairing of wires occurs when the wire-wire separation distance is reduced below some critical value. The wire pairing leads to wire jumps on the wire guide rolls, and if the run is not stopped, it leads to wire breakage. Moreover, it effectively obstructs the production of wafers thinner than the critical wire-wire distance. We suggest that the physical explanation to the observed limitations to ultrathin wafer sawing, by diamond multi-wire saw, is related to the capillary force acting on the wires due to the sawing liquid bridge connecting the wires. The hypothesis is supported by simplified mathematical modelling including capillary and spring forces between infinitely long, parallel wires. The calculations suggest that capillary forces are the main reason for wire pairing, and that wire pairing will occur when the wire distance is below some critical distance. This matches the observed, experimental behavior. The critical distance will vary with wafer saw design and operation. To succeed with cutting very thin wafers, we recommend using lower surface tension sawing fluid or even dry in-cut, to reduce the capillary forces and thus decrease the critical wire separation distance, and to reduce wire oscillations to decrease the probability of sub-critical wire-wire separation distance. To reduce the vibration amplitude, shorter distance between the wire guide rolls, thinner wires, and increased wire tension are suggested

Capillary forces as a limiting factor for sawing of ultrathin silicon wafers by diamond multi-wire saw

Succeeding with ultrathin silicon wafer sawing by diamond multi-wire saw, is not only a matter of optimization; the challenges of thin wafer production and the capability limit have not yet been fully understood. In this work, we have seen that regular pairing of wires occurs when the wire-wire separation distance is reduced below some critical value. The wire pairing leads to wire jumps on the wire guide rolls, and if the run is not stopped, it leads to wire breakage. Moreover, it effectively obstructs the production of wafers thinner than the critical wire-wire distance. We suggest that the physical explanation to the observed limitations to ultrathin wafer sawing, by diamond multi-wire saw, is related to the capillary force acting on the wires due to the sawing liquid bridge connecting the wires. The hypothesis is supported by simplified mathematical modelling including capillary and spring forces between infinitely long, parallel wires. The calculations suggest that capillary forces are the main reason for wire pairing, and that wire pairing will occur when the wire distance is below some critical distance. This matches the observed, experimental behavior. The critical distance will vary with wafer saw design and operation. To succeed with cutting very thin wafers, we recommend using lower surface tension sawing fluid or even dry in-cut, to reduce the capillary forces and thus decrease the critical wire separation distance, and to reduce wire oscillations to decrease the probability of sub-critical wire-wire separation distance. To reduce the vibration amplitude, shorter distance between the wire guide rolls, thinner wires, and increased wire tension are suggested