Using Micro-Raman Spectroscopy to Assess MEMS Si/SiO2 Membranes Exhibiting Negative Spring Constant Behavior

We introduce a novel micro-mechanical structure that exhibits two regions of stable linear positive and negative stiffness. Springs, cantilevers, beams and any other geometry that display an increasing return force that is proportional to the displacement can be considered to have a “Hookean” positive spring constant, or stiffness. Less well known is the opposite characteristic of a reducing return force for a given deflection, or negative stiffness. Unfortunately many simple negative stiffness structures exhibit unstable buckling and require additional moving components during deflection to avoid deforming out of its useful shape. In Micro-Electro-Mechanical Systems (MEMS) devices, buckling caused by stress at the interface of silicon and thermally grown SiO2 causes tensile and compressive forces that will warp structures if the silicon layer is thin enough. The 1 mm2 membrane structures presented here utilizes this effect but overcome this limitation and empirically demonstrates linearity in both regions. The Si/SiO2 membranes presented deflect ~17 μm from their pre-released position. The load deflection curves produced exhibit positive linear stiffness with an inflection point holding nearly constant with a slight negative stiffness. Depositing a 0.05 μm titanium and 0.3 μm layer of gold on top of the Si/SiO2 membrane reduces the initial deflection to ~13.5 μm. However, the load deflection curve produced illustrates both a linear positive and negative spring constant with a fairly sharp inflection point. These results are potentially useful to selectively tune the spring constant of mechanical structures used in MEMS. The structures presented are manufactured using typical micromachining techniques and can be fabricated in-situ with other MEMS devices

Stress Monitoring of Post-processed MEMS Silicon Microbridge Structures Using Raman Spectroscopy

Inherent residual stresses during material deposition can have profound effects on the functionality and reliability of fabricated Micro-Electro-Mechanical Systems (MEMS) devices. Residual stress often causes device failure due to curling, buckling, or fracture. Typically, the material properties of thin films used in surface micromachining are not well controlled during deposition. The residual stress; for example, tends to vary significantly for different deposition methods. Currently, few nondestructive techniques are available to measure residual stress in MEMS devices prior to the final release etch. In this research, micro-Raman spectroscopy is used to measure the residual stresses in polysilicon MEMS microbridge devices. This measurement technique was selected since it is nondestructive, fast, and provides the potential for in-situ stress monitoring. Raman spectroscopy residual stress profiles on unreleased and released MEMS microbridge beams are compared to analytical and FEM models to assess the viability of micro-Raman spectroscopy as an in-situ stress measurement technique. Raman spectroscopy was used during post-processing phosphorus ion implants on unreleased MEMS devices to investigate and monitor residual stress levels at key points during the post-processing sequences. As observed through Raman stress profiles and verified using on-chip test structures, the post-processing implants and accompanying anneals resulted in residual stress relaxation of over 90%

Baseline differences and intervention effects of the “Gesund und Glücklich Aufwachsen (GUG-Auf)” prevention program for children of depressed parents

Since children with a parent suffering from depression are at heightened risk of developing psychiatric disorders themselves, they are a target group for preventive interventions and as such a major public health priority. The cognitive-behavioural, family-, and group-based prevention program “Raising Healthy Children” (RHC) has shown promising findings in reducing the prevalence of depression and general psychopathology in a sample of children of depressed parents in the United States of America. The overarching aim of the current thesis is the evaluation of a German adaption of RHC prevention program. The current study is in this form unique, because the program was not evaluated yet outside the research group on an international level. In the first step I investigated whether the psychopathology of children of depressed parents is associated with parental depression (number of symptoms, number of depressive episodes), number of stressful experiences the child experienced and the parental socio-economic status (SES). For baseline differences, data of 77 families (who took part in an intervention study) were available, which were included in the analyses. There was no evidence that children of depressed parents differ at baseline in depressive symptoms in relation to parent depression severity, number of depressive episodes, the number of stressful experiences or the SES. But evidence emerged that offspring’s externalising problem behaviour is related to the number of parental depressive episodes, and offspring’s general psychopathology is related to the number of stressful life events. No relation between SES and offspring’s mental health could be demonstrated. In a second step, I examined whether the prevention program is effective in reducing child’s depression in the short-term (six months after baseline). By investigating preliminary data on incidence of depression at 15 months after baseline, I also investigated the extent to which the intervention prevented depression in the long-term. Further key aims were to see whether the program is effective in reducing child’s general psychopathology, and whether the program is effective in enhancing child’s knowledge of depression as well as whether it is effective in changing the parenting style in a positive direction in the short- and medium-term (six and nine months after baseline). The study was conducted as randomised controlled trial. The 77 families were randomised to receive the twelve session intervention vs. waiting list. Intervention outcomes suggested that the program has positive effects from child’s perspective on child’s internalising and mixed psychopathological symptoms. However, the parental view did not confirm these findings. Parent reports indicate that independent of group (intervention vs. waiting list) both symptom scales improved over a period of nine months. No evidence was found that the program shows benefits on child’s depression, knowledge of depression or child’s perception of parenting style. The knowledge of depression rather enhanced in short-term independent of participation. A feedback evaluation suggested that the general acceptability of the prevention program is high. The baseline findings indicate that the psychopathology of children of depressed parents is influenced by some, but not all, parental factors. Although I could not demonstrate the prevention effect of the program for depression prevention, I could show that some general psychopathological symptoms of children can be reduced by the program. The study provides an important step in the development of more effective prevention, which is exigently required

A Theology Built on Meritocracy: A Theological and Sociological Examination of the Prosperity Gospel and the American Dream

In American megachurch Christianity there lies a paradox in the concept of wealth and blessings; many megachurch leaders take deliberate steps to distance themselves from the defamed and heretical label of prosperity gospel, while simultaneously using many of its theological tenets as foundational to their own theology of wealth, money, and success. This thesis examines the nature of this paradox from both a theological and sociological lens. Through content analysis and case study examples, this thesis assesses the theological tenets of American megachurch prosperity theology as well as the sociological reality of stratification and the ideology that buttresses it. This work shows the paralleled nature of the paradox of prosperity and the American society’s belief in a meritocracy. The thesis explains that American megachurch Christianity’s overt and covert prosperity gospel themes are simply a religiously coded form of the American meritocratic ideology. The results call for religious leaders to identify this reality and work to correct the negative ramifications of it, while concurrently calling for more inquiry into the ways in which the American social stratification structure has become embedded in and maintained by religious systems

Now You See It, Now You Don\u27t: The Emerging Use of Ephemeral Messaging Apps by State and Local Government Officials

Public access to government-related information is essential in a democracy. The public expects state and local governments to function in an open and transparent manner to ensure accountability. All fifty states have adopted statutes that provide public access to government-related information. However, these statutes have not kept pace with changing technology. The emerging use of ephemeral messaging apps by state and local government officials presents an especially difficult problem. Ephemeral messaging apps are typically used on personal electronic devices, such as privately-owned smartphones. Unlike traditional text messages, however, ephemeral messages cannot be stored and subsequently accessed by the public. Rather, ephemeral messages self-destruct shortly after they are accessed by the recipient. Thus, it is not clear if ephemeral messages are public records—even if the messages pertain to government-related actions. A pending lawsuit in Missouri that pertains to the use of an ephemeral messaging app by former Governor Eric Greitens and members of his staff may be the first case in the nation to address this issue at the state and local level. Two recent state supreme court decisions from California and Washington concluded that traditional text messages that pertain to government-related actions may be public records even when they are retained on personal electronic devices or on third-party servers. These court decisions may provide some useful guidance with respect to ephemeral messages, but there are some key distinctions between traditional text messages and ephemeral messages. To avoid ambiguity and litigation, state legislatures should revise their public records statutes to make it clear that ephemeral messages that pertain to government-related actions are public records. If ephemeral messages cannot be stored and retrieved to ensure public access to this information, state legislatures should restrict the use of ephemeral messaging apps by public officials

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

On the stability of the recently developed nice integration scheme

The paper deals with the integration of elasto-plastic constitutive models using recently developed NICE integration scheme [1],[2]. The emphasis is put on the stability of the integration, since this issue was not sufficiently addressed in previous publications of the NICE. Nonlinear boundary value problems are nowadays typically solved numerically using finite element method (FEM) with implicit “static” (e.g. ABAQUS/Standard) or explicit “dynamic” approach (e.g. ABAQUS/Explicit). The NICE scheme was primarily developed for the integration of elasto-plastic constitutive models within explicit integration of a given boundary value problem, as a replacement for traditionally used backward-Euler scheme. The simplicity of the implementation, more than satisfactory accuracy and low time consumption of calculation, certainly outperforms the properties of other available schemes, including properties of the backward-Euler scheme. The only open issue regarding the NICE scheme is its conditional stability, which originates from the integration of evolution equations in a “forward” manner, whereas the backward-Euler scheme exhibits unconditional stability. The aim of this paper is to derive stable time increment for the NICE scheme and to show, that for practical quasi-static applications it is much larger than the stable time increment size given for the integration of dynamic boundary value problem equations

Characterization of Residual Stress in Microelectromechanical Systems (MEMS) Devices Using Raman Spectroscopy

Due to the small scale of MEMS devices, the inherent residual stresses during the deposition processes can affect the functionality and reliability of the fabricated devices. Residual stress often causes device failure due to curling, buckling, or fracture. Currently, few techniques are available to measure the residual stress in MEMS devices. In this dissertation, Raman spectroscopy is used to measure and monitor the residual and induced stresses in MUMPs polysilicon MEMS devices. Raman spectroscopy was selected since it is nondestructive, fast, and provides potential in situ stress monitoring. Raman spectroscopy scans on unreleased and released MEMS fixed-fixed beams, cantilevers, and micromirror flexures were performed to obtain residual stress profiles. The profiles are compared to analytical models to assess the accuracy of Raman spectroscopy. I performed post-processing thermal anneals, phosphorous diffusions and phosphorous ion implantations to characterize the residual stress changes within MEMS devices. From post-processing experiments, the Raman residual stress profiles on MUMPs structures indicate a stress reduction by over 90%, which is verified with on-chip test structures. The reduced residual stress levels can improve the performance, reliability, and yield of the MEMS devices as they become smaller. In addition, I present the first Raman stress measurements in III-V MEMS

Effect of Hyperons on Pion Asymmetries Measured in the Qweak Experiment

Experimental nuclear physics has largely been concerned with testing the Standard Model of particle physics. The Qweak experiment was designed to measure the weak interaction force of the proton. The experiment was also used to make asymmetry measurements on pions produced by inelastic collisions. The asymmetry measured in the experiment for pions was larger than expected at lower momentums given the kinematic conditions. A possible cause for the larger asymmetry is the production of hyperons, which decay into pions that can be detected. This idea was investigated, and an acceptance function for these pions was formulated. The acceptance function took the form of a four dimensional vector structure based on the probability of the pions being detected based on their initial kinetic energy, θ angle, φ angle, and z position