The Phase Change Memories (PCM) based on chalcogenide glasses are being considered recently as a possible replacement for conventional Non Volatile Random Access Memories (NVRAM). The main advantages of chalcogenide phase change memories are their direct write/overwrite capability, lower voltages of operation, large write/erase cycles, easiness to integrate with logic, etc. The phase change random access memories work on the principle of memory switching exhibited by chalcogenide glasses during which a local structural change (between amorphous and crystalline states) occurs due to an applied electric field. The development of newer phase change materials for NVRAM applications is based on synthesizing newer glass compositions and investigating their electrical switching characteristics by applying current/voltage pulses of different waveforms. The thermal studies on chalcogenide glasses which provide information about thermal stability, glass forming ability, etc., are also important while selecting a chalcogenide glass for PCM applications. The present thesis work deals with electrical switching and thermal studies on certain silicon based ternary telluride glasses (As-Te-Si, Ge-Te-Si and Al-Te-Si). The effect of network topological thresholds on the composition dependence of switching voltages and thermal parameters such as glass transition temperature, specific heat capacity, non-reversing enthalpy, etc., of these glasses has been investigated. The first chapter of the thesis provides an introduction to various properties of chalcogenide glasses, including their applications in phase change memories. The fundamental aspects of amorphous solids such as glass formation, glass transition, etc., are presented. Further, the concepts of rigidity percolation and self organization in glassy networks and the influence of local structural effects on the properties of glassy chalcogenides are discussed. Also, a brief history of evolution of phase change memories is presented. The second chapter deals with the experimental techniques employed in this thesis work; for sample preparation and for electrical switching studies, Alternating Differential Scanning Calorimetry (ADSC), Raman spectroscopy, NMR spectroscopy, etc. The third chapter discusses the electrical switching and thermal studies on As30Te70-xSix (2 ≤ x ≤ 22) and As40Te60-xSix (2 ≤ x ≤ 17) glasses. The composition dependence of electrical switching voltage (VT) and thermal parameters such as glass transition temperature (Tg), crystallization temperature (Tc), thermal stability (Tc-Tg), etc., reveals the occurrence of extended rigidity percolation and chemical thresholds in As30Te70-xSix and As40Te60-xSix glasses. Chapter 4 presents the electrical switching and thermal studies on Ge15Te85-xSix glasses (2 ≤ x ≤ 12). These glasses have been found to exhibit memory type electrical switching. While Ge15Te85-xSix glasses with x ≤ 5 exhibit a normal electrical switching, an unstable behavior is seen in the I-V characteristics of Ge15Te85-xSix glasses with x > 5 during the transition to ON state. Further, the switching voltage (VT) and initial resistance (R) are found to increase with addition of Si, exhibiting a change in slope at the rigidity percolation threshold of the Ge15Te85-xSix system. The ADSC studies on these glasses indicate the presence of an extended stiffness transition and a thermally reversing window in Ge15Te85-xSix in the composition range of 2 ≤ x ≤ 6. The fifth chapter deals with electrical switching investigations, thermal and structural studies on Al15Te85-xSix glasses (2 ≤ x ≤ 12). These glasses have been found to exhibit two crystallization reactions (Tc1 and Tc2) for compositions with x < 8 and a single stage crystallization is seen for compositions above x = 8. Also, a trough is seen in the composition dependence of non-reversing enthalpy (ΔHNR), based on which it is proposed that there is a thermally reversing window in Al15Te85-xSix glasses in the composition range 4 ≤ x ≤ 8. Further, Al15Te85-xSix glasses are found to exhibit a threshold type electrical switching at ON state currents less than 2 mA. The start and the end of the thermally reversing window seen in the thermal studies are exemplified by a kink and saturation in the composition dependence of switching voltages respectively. 27Al Solid State NMR measurements reveal that in Al15Te85-xSix glasses, Al atoms reside in 4-fold as well as 6-fold coordinated environments. Unlike in Al-As-Te glasses, there is no correlation seen between the composition dependence of the fraction of 4-fold and 6-fold coordinated aluminum atoms and the switching behavior of Al-Te-Si samples. Chapter 6 provides a comparison of the properties of the three glassy systems studied (As-Te-Si, Ge-Te-Si and Al-Te-Si), made to identify the system better suited for phase change memory applications. It is found that the Ge-Te-Si glassy system has better electrical/thermal properties for phase change memory applications. The seventh chapter describes easily reversible SET-RESET processes in Ge15Te83Si2 glass which is a promising candidate for phase change memory applications. This sample exhibits memory switching at a comparatively low threshold electric field (Eth) of 7.3 kV/cm. The SET and RESET processes have been achieved with 1 mA triangular current pulse for the SET process and 1 mA rectangle pulse (of 10 msec width) for RESET operation respectively. Further, a self-resetting effect is seen in this material upon excitation with a saw-tooth/square pulse. About 6.5x104 SET-RESET cycles have been achieved without any damage to the device. In chapter 8, results of in-situ Raman scattering studies on the structural changes occurring during the SET and RESET processes in Ge15Te83Si2 sample, are presented. It is found that the degree of disorder in the glass is reduced from OFF to SET state. The local structure of the sample under RESET condition is similar to that in the OFF state. The Raman results are found to be consistent with the switching results which indicate that the Ge15Te83Si2 glass can be SET and RESET easily. Further, Electron Microscopic studies on switched samples indicate the formation of nanometer sized particles of cSiTe2. A summary of the results obtained and the scope for future work are included in the chapter 9 of the thesis.

Den här kandidatuppsatsen har utförts genom en nulägesanalys på ett IT-inriktat konsultbolag. Studien identifierar det upplevda nuläget inom organisationen för att se om medarbetarnas upplevelser matchar de förhoppningar organisationen har med ett nytt infört värdegrundskoncept. Ett värdegrundskoncept med syfte att identifiera medarbetarnas inre motivation och främja den personliga utvecklingen samt hur det nya värdegrundskonceptet ämnar lösa de problem som finns inom system- och mjukvaruutveckling. Organisationen vill i sin tur att det ska leda till ett internt och externt värdeskapande och engagemang för alla parter, vilket kopplas till samhällsnytta, hållbarhet samt arbetsmiljö.   Studien har genomförts med en induktiv ansats, där den kvalitativa undersökningen har samlat in data utifrån sex intervjuer, för att få en djupare förståelse av medarbetarnas egna tankar och åsikter. Den insamlade empirin har sedan jämförts, analyserat och diskuteras i förhållande till teori och tidigare forskning. Utifrån likheter och skillnader kunde vi sedan dra en slutsats till hur nuläget i organisationen är i förhållande till vad teorin säger.   Resultatet av studien påvisar att respondenterna har en gemensam syn på att organisationen är innovativa och placerar medarbetarna i fokus. Inom organisationen finns det en samhörighet, lyhördhet och delaktighet, vilket skapar engagemang, motivation och personlig utveckling bland medarbetarna. Respondenterna ser det nya värdegrundskonceptet som ett bra komplement den agila metodiken som råder inom organisationen samt ett bra agilt verktyg. Organisationskulturen speglas av bra stämning, fräsch och inbjudande kontorsmiljö samt ärlighet mot kunden. Det framkom även en del meningsskiljaktigheter under undersökningen, exempelvis rörande osäkerhet över hur informationen tillhandahålls och hanteras. / This candidate assignment has been conducted through a zero-position analysis at an IT- based consulting company. The study identifies the current situation within the organization to see if the employees' experiences match the hopes the organization has with a new introduced values concepts. A values concepts aimed at identifying employees' internal motivation and promoting personal development as well as how the new values concepts aims to solve the problems in system and software development. The organization, in turn, wants it to lead to internal and external value creation and commitment for all parties, linked to community benefits, sustainability and work environment.   The study has been conducted with an inductive approach, where the qualitative survey has collected data based on six interviews, to gain a deeper understanding of the employees' own thoughts and opinions. The collected empire has since been compared, analyzed and discussed in relation to theory and previous research. Based on similarities and differences, we could then draw a conclusion about how the present situation in the organization is in relation to what the theory says.   The result of the study shows that respondents have a common view that the organization is innovative and places employees in focus. Within the organization there is a sense of togetherness, responsiveness and participation, which creates commitment, motivation and personal development among the employees. Respondents see the new values concepts as a good complement to the agile methodology within the organization as well as a good agile tool. The organizational culture is reflected by good atmosphere, fresh and inviting office environment and honesty towards the customer. There were also some differences of opinion during the investigation, such as uncertainty about how the information is provided and managed.