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High performance and low cost sensors based on microelectromechanical systems (MEMS) have become commonplace in today's world. MEMS sensors, such as accelerometers, gy- roscopes, pressure sensors, and microphones, are routinely used in consumer electronics, automobiles, industrial and aerospace applications. Basically, all these devices mea- sure tiny displacements of micromachined mechanical structures in response to external stimuli. One of the widely used techniques to detect these displacements is piezoresistive sensing. Piezoresistive sensors are popular in MEMS due to their simplicity and robustness. Traditionally, silicon has been the material of choice for piezoresistors due to its high strain sensitivity or gauge factor. Whereas metal lm piezoresistors typically have low gauge factor that puts them out of favour when compared to silicon. But metal lm piezoresistors have several advantages compared to their semiconductor counterparts, including simple and low-cost fabrication, low resistivity and generally low noise. Low resistance sensors become desirable particularly when the devices are scaled down to nanoelectromechanical systems (NEMS), where signal-to-noise ratio (SNR) performance becomes crucial. Enhancing the gauge factor of metal lms while keeping their low resistance advantage can dramatically improve their SNR performance for NEMS. This thesis reports a simple method we have developed to enhance the gauge factor of metal lm piezoresistors. We demonstrate this method on specially designed micro- cantilever devices. Using controlled electromigration, we are able to engineer the microstructure of gold lm and transform it into a locally inhomogeneous conductor which resembles a percolation network. This results in more than 100 times higher gauge factor at low to moderate sensor resistance. The SNR possible with our piezoresistor at high frequencies exceeds that of most available systems by at least an order of magnitude. Our locally inhomogeneous metal lm piezoresistor is a promising candidate for high-performance NEMS-based sensors of the future.

We report approaches to grow ultrathin Ru films for application as a seed layer and Cu diffusion barrier. For chemical vapor deposition (CVD) with Ru3(CO)12 we show the role surface hydroxyl groups have in nucleating the Ru islands that grow into a continuous film in a Volmer-Weber process, and how the nucleation density can be increased by applying a CO or NH3 overpressure. Thinner continuous films evolve in the presence of a CO overpressure. We report an optimun ammonia overpressure for Ru nucleation and that leads to deposition of smoother Ru thin films. Finally, we report a comparison of amorphous Ru films that are alloyed with P or B and demonstrate 3-nm thick amorphous Ru(B) films function as a Cu diffusion barrier.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-11-07T17:37:23Z No. of bitstreams: 1 GUTEMBERGUE FERNANDES FELIX – DISSERTAÇÃO (PPGFísica) 2015.pdf: 4186541 bytes, checksum: 4a3992774386ae9b9cbe14133dd60146 (MD5) / Made available in DSpace on 2018-11-07T17:37:23Z (GMT). No. of bitstreams: 1 GUTEMBERGUE FERNANDES FELIX – DISSERTAÇÃO (PPGFísica) 2015.pdf: 4186541 bytes, checksum: 4a3992774386ae9b9cbe14133dd60146 (MD5) Previous issue date: 2015-09-15 / Capes / Nosso trabalho tem como objeto de estudo as interações entre átomos de césio e uma superfície dielétrica. Essas interações são do tipo vanderwaals, atrativas de longo alcance e do tipo Pauli, repulsiva sem curtas distâncias. Este trabalho é composto pela análise do crescimento de filmes térmicos e a análise da dessorção de filmes induzidos por luz. Procuramos compreender: Como é a organização da sobreposição para formar um filme metálico sobre a superfície. Nós apresentamos os procedimentos utilizados e o aparato experimental para medir a dessorção de filmes induzidos por luz. Descrevemos cada procedimento realizado para obtenção das medidas, bem como as etapas de análise dos resultados. Neste trabalho discutimos os modelos mais conhecidos de adsorção, o modelo de Langmuir e o modelo BET.A partir da análise dos dados experimentais de adsorção térmica, constatamos que os dados se ajustam na descrição de filmes que crescem em multicamadas sobre a superfície. Através da análise das curvas de dessorção de filmes induzidos por luz podemos obter valores da energia de adsorção. A principal pergunta que queremos responder é: qual a energia de adsorção para um filme induzido por luz. Os valores obtidos para a energia de adsorção de filmes induzidos por luz (cerca de 0,80 e V) são maiores que as energias de adsorção física (estas em torno de 0,40 e V-0,50 e V) e perto da energia de condensação do césio. / In our work we studied the interactions between cesium atoms and a dielectric surface. These interactions are known as the type Vander Waals attractive at long-range and Pauli type, repulsive ats hort distances. This work is divided in to two parts. In the first part we made the analysis of growth of thermal films and we made in the second partthe analysis of films induced by light. Our objetive is understand how is the organization of atoms to form a metallic film on the surface. We describe the procedures used and the experimental apparat us to measure the desorption of films induced by light. We present how each procedure is performed to obtain the measurements and the results of analysis. In this work we present the best known models for adsorption the Langmuir model and the BET model. By analyzing experimental data of thermal absorption we could observe that the data fits in the description of films that grow in multilayers on the surface. We make the analysis of desorption of films induced by light and we get the adsorption energy values. Our main objective is find the value of the adsorption energy for a film induced by light. The values obtained for the adsorption energy to films induced by light (about 0.80 e V) is higher than the energies of physical adsorption (these around 0.40 e V-0.50 e V) and close to the energy of cesium condensation.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21764号 / 工博第4581号 / 新制||工||1714(附属図書館) / 京都大学大学院工学研究科原子核工学専攻 / (主査)教授 功刀 資彰, 教授 横峯 健彦, 教授 村上 定義 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Part A: The preliminary investigation of the thermal and electrical behaviour of thin metal films gives evidence, Part I, that several mechanisms are responsible for the change of resistance as the temperature increases from room temperature to 500°C. Firstly, there appears grain growth giving a characteristic decrease in resistance. Secondly, the formation of agglomerates upon the continued growth of grains; especially for the thinner Al and Cr films. This effect tends to increase the resistance and a mathematical model is proposed to explain the results qualitatively. Thirdly, the occurrence of what appeared to be an electromigration effect. This latter point provided the incentive for a study on the effects of electromigration in thin aluminum film, Part II. The results of this study are comparable to those obtained by other workers, except that the interpretation for the direction of electromigration in Al is reversed. One possible explanation for the difference in the direction of migration could be due to the interpretation of marker motion. A mathematical model is also proposed for electromigration, in which both the effects due to the applied electric field and the electrons collision with the ions have been taken into consideration. It was found that the effect due to electrons collision with the ions upon the migration of ions could be expressed in terms of an exponential function of the square of the electron to ion collision relaxation time. / Thesis / Master of Engineering (ME)

Reliability, besides the performance, is one of the important key factors of success of any technology. While a product should perform at best as desired, it must also be capable of working for intended period of life without any degradation or wear-out failure, caused by any operational parameter. For example it does no good to manufacture a super fast microprocessor if that fails within few seconds. For the product to meet the intended reliability we must understand the mechanisms that lead to unreliability or failure of the devices. The efforts to understand the fundamental physics of the mechanisms that lead to the failure of the devices has developed a branch of physics named as “reliability physics” of “physics of failure”. On the basis of the understanding of failure mechanism, new design rule can be followed and new material can be applied to improve the reliability of the product. Microelectronic technology also, which is one of the fastest growing technology, has been facing challenges posed by the reliability issues from time to time. There are number of physical failure mechanisms that can affect the reliability of a microelectronic device. Time dependent dielectric breakdown (TDDB), hot carrier damage and current induced damage of interconnects are only to name a few common mechanisms. Among these, the failure of interconnects due to current has been the oldest and persistence reliability issue since the beginning of development of the microelectronic technology. Understanding the physics of the processes that lead to failure of a current carrying film is the main interest of this thesis work. In this investigation, we have carried out a systematic study to understand stability of metal nanowires against damage caused by current stressing and its size dependency. We observe the wires of smaller diameter, having an electronic mean free path larger than or comparable to its diameter are more stable against current stressing. In wires of larger diameter (100 nm or more) the probability of the damage is more. This probably is due to presence of grain boundary type extended defects that allow low energy diffusion path. To our knowledge this is the first experimental investigation to study the stability of nanowires against high current and in-situ measurement of noise during current stressing on them. In the previous investigations by other groups observed that the nanowires without any passivation got damaged by stressing current density which was even lower than the one we used for stressing. To our knowledge this is the first observation of long lasting stability of nanowires, of dimension down to 15 nm, when they are encapsulated in dielectric, an environment that an interconnect has to see in the real integrated circuit devices. In the second chapter we will describe the sample preparation method, characterization of samples and the experimental setups we had used. The results of in-situ noise measurement are described in the third chapter. We will describe our in-situ scanning thermal microscopy study in the fourth chapter. Then in the fifth chapter, we will present our simulation investigations on current induced damage of film. Finally, we will put the concluding remarks on this thesis work and the results in the sixth chapter. We have studied similar damage processes in metal nanowires also. In an appendix we will present our approach and major results of this investigation.

We report approaches to grow ultrathin Ru films for application as a seed layer and Cu diffusion barrier. For chemical vapor deposition (CVD) with Ru3(CO)12 we show the role surface hydroxyl groups have in nucleating the Ru islands that grow into a continuous film in a Volmer-Weber process, and how the nucleation density can be increased by applying a CO or NH3 overpressure. Thinner continuous films evolve in the presence of a CO overpressure. We report an optimun ammonia overpressure for Ru nucleation and that leads to deposition of smoother Ru thin films. Finally, we report a comparison of amorphous Ru films that are alloyed with P or B and demonstrate 3-nm thick amorphous Ru(B) films function as a Cu diffusion barrier.

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.