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Current magnetic data storage technology is encountering certain fundamental limitations that present roadblocks to its scalability to areal densities of 1 Tbit/in^2 and beyond. Next generation magnetic storage technology is expected to use optical near field techniques to heat the magnetic film locally to write data bits. This requires experimental measurement of thermal conductivity of materials with sub--100 nm resolution. This is essential for the tailoring of the thin film stack to optimize the heat transfer of the process. This can be accomplished with a simple modification to a traditional atomic force microscopy (AFM) system. The modification requires the deposition of a thin metal film on the AFM cantilever thus creating a bimetallic cantilever. The curvature of a bimetallic cantilever is sensitive to temperature. Another modification is the use of a heating laser to raise the temperature of the cantilever so that when it scans across a sample with areas of varying thermal conductivity the bimetallic deformation of the heated cantilever is altered. The resulting system is sensitive to local variations in thermal conductivity with nanoscale resolution. Nanoscale thermal conductivity measurements can then be used to optimize the heat transfer properties of the materials used in a heat assisted magnetic recording system. AFM technology can also play a key role in the development of next generation solid-state chemical sensors. An AFM can be used to measure the workfunction of a material with near atomic resolution thus enabling the study of chemical reactions with high spatial resolution. Since chemical sensors typically use a chemical reaction at their front end to monitor the prescience of a gas, an AFM system can thus be used to understand and optimize the properties of the chemical reaction by monitoring the local workfunction. In this thesis, I explain the use of atomic force microscopy in measuring thermal and chemical properties of materials with applications towards the magnetic storage industry and chemical sensing.

Two-dimensional graphene, a single layer of graphite, has emerged as an excellent candidate for future electronic material due to its unique electronic structure and remarkably high carrier mobility. Even higher carrier mobility has been demonstrated in graphene devices using hexagonal boron nitride as an underlying dielectric support instead of silicon oxide. Interestingly, both graphene and boron nitride exhibit superior thermal properties, therefore may potentially offer a solution to the increasingly severe heat dissipation problem in nanoelectronics caused by increased power density. In this thesis, we focus on the investigation of the thermal properties of graphene and hexagonal boron nitride. First, scanning thermal microscopy based on a sub-micrometer thermocouple at the apex of a microfabricated tip was employed to image the temperature profiles in electrically biased graphene devices with ~ 100 nm scale spatial resolution. Non-uniform temperature distribution in the devices was observed, and the "hot spot" locations were correlated with the charge concentrations in the channel, which could be controlled by both gate and drain-source biases. Hybrid contact and lift mode scanning has enabled us to obtain the quantitative temperature profiles, which were compared with the profiles obtained from Raman-based thermometry. The temperature rise in the channel provided an important insight into the heat dissipation mechanism in Joule-heated graphene devices. Next, thermal conductivity of suspended single and few-layer graphene was measured using a micro-bridge device with built-in resistance thermometers. Polymer-assisted transfer technique was developed to suspend graphene layers on the pre-fabricated device. The room temperature thermal conductivity values of 1-7 layer graphene were measured to be lower than that of bulk graphite, and the value appeared to increase with increasing sample thickness. These observations can be explained by the impact of the phonon scattering by polymer residue remaining on the sample surfaces. Lastly, thermal conductivity of few-layer hexagonal boron nitride sample was measured by using the same device and technique used for suspended graphene. Measurements on samples with different suspended lengths but similar thickness allowed us to extract the intrinsic thermal conductivity of the samples as well as the contribution of contact thermal resistance to the overall thermal measurement. The room temperature thermal conductivity of 11 layer sample approaches the basal-plane value reported in the bulk sample. Lower thermal conductivity was measured in a 5 layer sample than an 11 layer sample, which again supports the polymer effect on the thermal transport in few-layer hexagonal boron nitride. / text

The Fluorescence Scanning Thermal Microscope (FSTM v3.0), was designed to create an inexpensive, and easily manufactured, device for measuring the diffusivity of samples with microscopic locational precision. This was accomplished by using a Blu-ray device known as a PHR-803T, referred to in this work as a PHR. The optics in the PHR are nearly identical in function to conventional devices used in thermoreflectance microscopy, making the PHR extremely useful to integrate into the FSTM design. The focus of this thesis is the application of the FSTM as a confocal microscope using 3D printed components and various low-cost devices to operate with comparable sampling accuracy to existing confocal microscopes. The electronics and optical filters were then adapted to enable the measurement of thermal waves, particularly by detecting a linear relationship between phase delay and the spacing between heating and sensing lasers, as predicted by previous work on the FSTM.

The crystalline solid state is invaluable to both the pharmaceutical and fine chemical sectors. The advantages primarily relate to reducibility criteria required during processing of stable solid state materials and delivering purification, which is inherently performed by the crystal growth process. A major challenge is achieving control through crystallising solids with the desired physico-chemical properties. If this can be achieved the crystalline solid is of great financial and practical benefit. One emerging methodology for manipulating the solid crystalline form is the application of co-crystals. This work relates to key steps in the understanding of rational design of co-crystals utilizing crystal engineering concepts to determine systems before then applying screening criteria to the selected sub-set. Co-crystal screening is routinely undertaken using high-throughput solution growth. We report a low- to medium-throughput approach, encompassing both a melt and solution crystallization step as a route to the identification of co-crystals. Prior to solution studies, a melt growth step was included utilizing the Kofler mixed fusion method. This method allowed elucidation of the thermodynamic landscape within the binary phase diagram and was found to increase overall screening efficiency. This led to the discovery of a number of co-crystal systems with the co-former nicotinamide, with the single crystal structures determined for the following systems; R/S ibuprofen: nicotinamide, S ibuprofen: nicotinamide, R/S flurbiprofen: nicotinamide and salicylic acid: nicotinamide. To assess the crystallization and phase behaviours of determined co-crystals the R/S ibuprofennicotinamide system was selected and successful studies were undertaken determining the aqueous ternary phase behavior and the pre-nucleation speciation in methanol. There have, as yet, been a limited number of published examples which are concerned with pharmaceutical property enhancement by co-crystals, as vast proportion of the literature concerns the growth and isolation of these novel phases. To elucidate further the pharmaceutical relevance of co-crystals the properties of the R/S ibuprofen- nicotinamide system were then assessed showing a positive profile for this material.

Dans les applications nucléaires, les propriétés des matériaux peuvent subir des modifications importantes en raison de l'interaction destructive avec l'irradiation de particules au niveau des microstructures, qui affectent les propriétés globales. L'un des défis associés aux études de matériaux irradiés par des ions, c'est que la couche concernée, ou la profondeur de pénétration, est généralement très mince (0,1-100 um). Cette étude élargit la base des connaissances actuelles en matière de transport thermique dans les matériaux irradiés par des ions, en utilisant une approche expérimentale multiéchelles avec des méthodes basées sur des ondes thermiques. D'une manière pas encore explorée auparavant, quatre méthodes sont utilisées pour caractériser la couche irradiée par des protons dans ZrC : la microscopie thermique à balayage (SThM), la radiométrie photothermique (PTR) avec détection sur la face avant et balayage spatial, la thermographie infrarouge lock-In (IRT), et la PTR tomographique avec balayage en fréquence. Pour la première fois, le profil de conductivité thermique en profondeur d'un échantillon irradié est mesuré directement. Les profils obtenus par chacune des méthodes d'analyse spatiale sont comparés les uns aux autres et à la prévision numérique du profil endommagé. La nature complémentaire des différentes techniques valide le profil mesuré et la dégradation constatée de la conductivité thermique de l'échantillon de ZrC. / In nuclear applications, material properties can undergo significant alteration due to destructive interaction with irradiating particles at microstructural levels that affect bulk properties. One of the challenges associated with studies of ion-Irradiated materials is that the affected layer, or penetration depth, is typically very thin (~0.1-100 μm). This study expands the current knowledge base regarding thermal transport in ion-Irradiated materials through the use of a multiscaled experimental approach using thermal wave methods. In a manner not previously explored, four thermal wave methods are used to characterize the proton-Irradiated layer in ZrC including scanning thermal microscopy (SThM), spatial-Scanning front-Detection photothermal radiometry (PTR), lock-In IR thermography (lock-In IRT), and tomographic, frequency-Based PTR. For the first time, the in-Depth thermal conductivity profile of an irradiated sample is measured directly. The profiles obtained by each of the spatial scanning methods are compared to each other and the numerical prediction of the ion-Damage profile. The complementary nature of the various techniques validates the measured profile and the measured degradation of thermal conductivity in the ZrC sample.

Le travail présenté dans cette thèse est une contribution pour progresser vers des mesures thermiques plus quantitatives. Il s'agit de mesurer la température par la technique RIF de l'émission verte. Les travaux réalisés dans ce mémoire s'articulent en trois étapes. Au départ nous avons mesuré la température d'échauffement d'un cristal massif Sr0.3Cd0.7F2 codopés Er3+/Yb3+ d'épaisseur 0.3 mm. L'échauffement induit par l'excitation des ions Yb3+ à 974.4 nm a été mesurée à une distance (d) au bord de cristal, par l'émission verte des ions Er3+ excité par le laser rouge (652 nm) au bord du cristal. La seconde étape a eu pour but la mesure de la température d'échauffement du même cristal précédent, mais en dimension microscopique. Ces microparticules fluorescentes ont été fixées à l'extrémité d'une sonde thermique de Wollaston. L'échauffement des microparticules se fait par une excitation laser rouge à 652 nm ou par effet Joule en parcourant un courant électrique dans la sonde thermorésistive. La troisième étape a eu pour principal objectif la mesure de la température à l'échelle micrométrique en utilisant un microscope à force atomique (AFM) sur lequel est montée une sonde thermorésistive munie à son extrémité d'une microparticule fluorescente de Sr0.3Cd0.7F2 codopée Er3+/Yb3+ de 15 µm utilisée comme capteur de température. La technique est basée sur la variation de l'intensité de la fluorescence de la microparticule en contact avec une surface chaude. Cette nouvelle technique nous a permis d'obtenir une image cartographique de la température d'un microsystème, composé de lignes chauffantes submicroniques, chauffé par effet Joule. / The work presented in this thesis is a contribution to progress towards more quantitative thermal measurements. This is to measure the temperature by RIF technique green emission. The work in this thesis is divided into three stages. Initially we measured the temperature rise of a massive crystal Sr0.3Cd0.7F2 codoped Er3 + / Yb3 + 0.3 mm thick. The heat induced by the excitation of Yb3 + ions to 974.4 nm was measured at a distance (d) at the edge of crystal, the green emission of the Er3 + ions excited by red laser (652 nm) at the edge of the crystal.The second step was designed to measure the temperature of the heating of the same previous crystal, but in microscopic dimensions. These fluorescent microparticles were attached to the end of a thermal probe Wollaston. The temperature rise of the microparticles is by a red laser excitation at 652 nm or by Joule effect through an electric current in the probe thermorésistive.The third step was the main aim of measuring the temperature using a micrometric scale atomic force microscope (AFM) on which is mounted at its end provided with one of a fluorescent microparticle thermorésistive probe Sr0.3Cd0.7F2 codoped Er 3 + / Yb 3 + 15 microns used as a temperature sensor. The technique is based on the change in fluorescence intensity of the microparticle in contact with a hot surface. This new technique allowed us to obtain a map image of the temperature of a microsystem consisting of submicron heating lines, heated by Joule effect.

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.

Scanning probe microscopes (SPMs) are the highest resolution imaging instruments available today and are among the most important tools in nanoscience. Conventional SPMs suffer from several drawbacks owing to their large and bulky construction and to the use of piezoelectric materials. Large scanners have low resonant frequencies that limit their achievable imaging bandwidth and render them susceptible to disturbance from ambient vibrations. Array approaches have been used to alleviate the bandwidth bottleneck; however as arrays are scaled upwards, the scanning speed must decline to accommodate larger payloads. In addition, the long mechanical path from the tip to the sample contributes thermal drift. Furthermore, intrinsic properties of piezoelectric materials result in creep and hysteresis, which contribute to image distortion. The tip-sample interaction signals are often measured with optical configurations that require large free-space paths, are cumbersome to align, and add to the high cost of state-of-the-art SPM systems. These shortcomings have stifled the widespread adoption of SPMs by the nanometrology community. Tiny, inexpensive, fast, stable and independent SPMs that do not incur bandwidth penalties upon array scaling would therefore be most welcome. The present research demonstrates, for the first time, that all of the mechanical and electrical components that are required for the SPM to capture an image can be scaled and integrated onto a single CMOS chip. Principles of microsystem design are applied to produce single-chip instruments that acquire images of underlying samples on their own, without the need for off-chip scanners or sensors. Furthermore, it is shown that the instruments enjoy a multitude of performance benefits that stem from CMOS-MEMS integration and volumetric scaling of scanners by a factor of 1 million. This dissertation details the design, fabrication and imaging results of the first single-chip contact-mode AFMs, with integrated piezoresistive strain sensing cantilevers and scanning in three degrees-of-freedom (DOFs). Static AFMs and quasi-static AFMs are both reported. This work also includes the development, fabrication and imaging results of the first single-chip dynamic AFMs, with integrated flexural resonant cantilevers and 3 DOF scanning. Single-chip Amplitude Modulation AFMs (AM-AFMs) and Frequency Modulation AFMs (FM-AFMs) are both shown to be capable of imaging samples without the need for any off-chip sensors or actuators. A method to increase the quality factor (Q-factor) of flexural resonators is introduced. The method relies on an internal energy pumping mechanism that is based on the interplay between electrical, mechanical, and thermal effects. To the best of the author???s knowledge, the devices that are designed to harness these effects possess the highest electromechanical Qs reported for flexural resonators operating in air; electrically measured Q is enhanced from ~50 to ~50,000 in one exemplary device. A physical explanation for the underlying mechanism is proposed. The design, fabrication, imaging, and tip-based lithographic patterning with the first single-chip Scanning Thermal Microscopes (SThMs) are also presented. In addition to 3 DOF scanning, these devices possess integrated, thermally isolated temperature sensors to detect heat transfer in the tip-sample region. Imaging is reported with thermocouple-based devices and patterning is reported with resistive heater/sensors. An ???isothermal electrothermal scanner??? is designed and fabricated, and a method to operate it is detailed. The mechanism, based on electrothermal actuation, maintains a constant temperature in a central location while positioning a payload over a range of >35??m, thereby suppressing the deleterious thermal crosstalk effects that have thus far plagued thermally actuated devices with integrated sensors. In the thesis, models are developed to guide the design of single-chip SPMs and to provide an interpretation of experimental results. The modelling efforts include lumped element model development for each component of single-chip SPMs in the electrical, thermal and mechanical domains. In addition, noise models are developed for various components of the instruments, including temperature-based position sensors, piezoresistive cantilevers, and digitally controlled positioning devices.

Ce mémoire de thèse s’inscrit dans le développement d’un microscope thermique à sonde locale.Ce système d’imagerie présente deux modes de fonctionnement permettant de déterminer soit unetempérature de surface soit des propriétés thermophysiques de matériaux. Un micro-thermocouplebifilaire a été utilisé comme capteur thermique. Il est peu invasif et permet d’accéder à destempératures de surface sur une large gamme de température. De plus, le microscope offrel’avantage d’être moins sensible à la nature optique des échantillons que les méthodes en champlointain. Dans le but de maitriser le contact entre la sonde et la surface, un résonateur à quartz(diapason) a été utilisé comme capteur de force. Un système d’excitation original basé sur l’effetphoto-thermo-élastique a été mis au point. Le microscope fonctionne donc comme un SThM puisqu’ilpermet d’extraire simultanément des images topographiques et thermiques (régime périodique 2 et3 oméga). En revanche, les résultats obtenus ont permis de mettre en évidence les avantages dumicro-thermocouple en termes de résolutions spatiales topographiques vis-à-vis des techniques àsondes résistives fonctionnant en mode 3 oméga. / This PhD thesis deals with the development of a thermalmicroscope using a local probe. This imagingsystem presents two functioning modes that allow determining either surface temperature or thermalproperties of materials. A micro-wire thermocouple is used as a thermal sensor. It is less invasiveand allows measuring the surface temperature with a large temperature range. Furthermore, themicroscope offers an advantage to be less sensitive to the optical nature of a sample surface thanoptical methods. To control the contact between the probe and the surface, a quartz tuning fork hasbeen used as a force sensor. An original excitation system has been developed based on the photothermaleffect. The microscope works also as a SThM since it permits to extract simultaneouslytopographical and thermal pictures (2 and 3 omega periodical modes). Results underlining themicro-thermocouple advantages, in terms of topographical compared to resistive probe techniquesfunctioning with the 3 omega method, have been obtained.