Since the first report of the Unibond process,l there has been much interest in reproducing Si exfoliation by H implantation and in understanding the mechanism leading to such a remarkably uniform shearing. We have previously demonstrated that, contrary to the initial speculation? there are in fact three distinct aspects to the process3 i) The generation of damage to the crystalline material by the implantation; ii) The unique surface chemistry of hydrogen and silicon that drives the thermal evolution of this damage region and; iii) The creation of internal pressure that ultimately causes exfoliation of the overlying Si layer. Therefore, a detailed understanding of the exfoliation mechanism involves the study of initial damage, of H-passivation of various internal structures and of the mechanical forces exerted by trapped gases as a function of hydrogen implantation doseldepth and annealing temperature. In this work, we have used different hydrogen implantation conditions (ion energies ranging from 1 V to 1 MeV and substrate crystallographic orientations) as well as co-implantation of a variety of other elemental species, in combination with novel spectroscopic configurations, to further explore these different mechanistic aspects.Infrared spectroscopy has played a key role in elucidating the microscopic details of the process, due to its high sensitivity and selectivity and inherent non-destructiveness. However, the frequency range accessible was limited to above 1500 cm-1 so that only the Si-H stretching vibrations could be observed. Recently, we have developed novel optical configurations that allow probing of the Si-H bending modes (at -600-650 cm-1) and scissor modes (850-910 cm-I), allowing definitive identification of the different defect modes. Using this approach, in combination with a variety of other techniques, we have been able to definitively show that exfoliation consists of the following distinct mechanistic steps: Above the critical dose of 6 x 1016/cm2, the IR spectrum shows evidence for monohydride-terminated, multi-vacancy defects that are typically found in hydrogenated amorphous silicon. The formation of such a "multivancy" defect region is critical to exfoliation, because it allows both formation of agglomerated defects and the evolution of molecular H2. These defects, in turn, develop into (100) and (1 11) internal cracks which act as traps for the H2 leading to the build-up of internal pressure and subsequent shearing. It is the synergetic combination of H-passivation of internal surfaces and H2 pressure within these intemal cracks that leads to the shearing in the presence of the joined wafer, that acts as a mechanical stiffener. Importantly, in the absence of the stiffener, the surface 'blisters'; in the absence of sufficient damage (below the critical dose), the hydrogen diffuses away from the implanted region, preventing exfoliation.Recent experiments4 have isolated the physical and chemical contributions to exfoliation by co-implanting He, Li and Si along with H and demonstrated that...

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There are a number of additional challenges in the development of high CO2 content gas fields. To meet the requirements of the Kyoto Protocol and Paris Agreement, an efficient means to deal with the produced CO2 such as re-injection into the reservoir for sequestration is required. With the intention of developing such high CO2 gas fields, PETRONAS has identified a trial candidate (X field) offshore Sarawak Malaysia, which is a carbonate gas field with 70% CO2 content and good potential to re-inject the produced CO2 into the field's aquifer zone. To study the feasibility of CO2 reinjection, PETRONAS R&D team are studying the effects of re-injected CO2 on the mineralogical and petrophysical properties of the reservoir and decided to incorporate Digital Core Analysis (DCA) into the case study. Although porosity determination and other petrophysical property characterisation using micro-CT images has been widely used for a number of years, there is still discussion about its accuracy and reliability. Based on previous internal studies, porosity determination via digital core analysis can be limited by the quality and resolution of micro-CT images collected and thus the capability of the image analysis software. This case study investigates accuracy and reliability of the use of contrast enhanced imaging practices and the use of the helical micro CT for porosity determination via Digital Core Analysis (DCA). PETRONAS adopted and optimized a contrast enhanced imaging methodology for use on 1-inch core plugs during scanning via a helical micro-CT and applied this as a case study to X field with the help of a technology partner to evaluated digital core analysis. In the same year, a commercially available image analysis software was launched, with such a DCA workflow in mind. Using this optimized methodology and the newly launched imaging software, the porosity values from DCA of the 1-inch core plugs show good correlation to the values from Routine Core Analysis (RCA) done on the same samples, with less than 1.5 porosity unit difference. In this case study, PETRONAS managed to compare the porosity obtained from DCA directly with porosity measured by RCA. This methodology will be used for porosity determination for wells or other regions of interest where limited samples or different sample sizes are not suitable for RCA.