Modulation of heterogeneous surface charge and flow pattern in electrically gated converging-diverging nanochannel

The present study aims at utilizing field effect phenomenon to induce heterogeneous surface charge and consequently changing the fluid flow in a solid state nanochannel with converging-diverging periodicity. It is shown that the proposed geometry causes non-uniform radial field adjacent to channel walls which is stronger around the diverging section and weaker next to the converging part of the wall. The later generates heterogeneous surface charge at channel walls depending on the applied gate potential i.e. applying low gate potential enables effective modulation of surface charge with the same polarity of the intrinsic charge at channel walls, while moderate gate potential causes charge inversion in diverging sections of the channel and generates reverse flow and thus results in fluid flow circulation. The potential application of flow circulation for trapping and rejection of particles is also demonstrated.Comment: 6 pages, 8 figure

Selective Epitaxy of Group IV Materials for CMOS Application

As the International Technology Roadmap for Semiconductors (ITRS) demands an increase of transistor density in the chip, the size of transistors has been continuously shrunk. In this evolution of transistor structure, different strain engineering methods were introduced to induce strain in the channel region. One of the most effective methods is applying embedded SiGe as stressor material in source and drain (S/D) regions by using selective epitaxy. This chapter presents an overview of implementation, modeling, and pattern dependency of selective epitaxy for S/D application in CMOS. The focus is also on the wafer in and ex situ cleaning prior to epitaxy, integrity of gate, and selectivity mode

Development of a wirelessly controlled drug delivery implantable chip based on IPMC actuator for cancer treatment

In the present study, the novel implantable drug delivery chip was designed by silicon reservoir and Ionic Polymer Metal Composite (IPMC) actuator integration. The whole design was tested to be biocompatible. The reservoir was developed by high technique silicon lithography and the IPMC strip was attached as the gate of the drug reservoir. The IPMC actuation and subsequently the drug release was controlled by a manipulated communication system based on transmitter and receiver circuits, designed for wireless power transmission. Electromagnetic waves with 2 MHz frequency were for power transmission. The wireless transmission is on the order of 5 cm due to the chip potential to get implanted in the patient's body, near the cancerous organ. Introduction: Drug delivery systems are divided into two main categories: passive systems and active systems, where the drug release is controlled by an external source. The active systems involve remote controlled drug delivery chips based on silicon, a remarkable technology, which releases a certain dose of drug on demand from outside the body. Both systems are designed to facilitate cancer treatment and prevent patients from getting involved with the chemotherapy's side effects. Methods and Results:IPMC was fabricated by electroless deposition of nafion as a smart polymer with the ability to bend in low applied voltages. The prepared IPMC was attached to an etched silicon as a single drug reservoir chip. The transmitter section included a microcontroller, a driver, an amplifier and a coil. Electromagnetic waves generated in the transmitter section were captured by the receiver section, converted to electrical voltage and transferred toIPMC actuator to unseal the drug reservoir.Figure 1 shows the schematic of the drug delivery chip with wireless communications. Conclusions:The single reservoir, wirelessly controlled drug delivery chip was designed using IPMC actuator as the gate of the reservoir. The drug was released on demand by generating electromagnetic waves that were converted to electrical voltage and transferred to IPMC actuator in receiver section on the chip

A comparative study of electrolyte concentration-symmetry and gate voltage effects on the heterogenous surface charge in a nanofluidic FET

Pre-print (óritrýnt handrit)The present study aims to investigate utilizing field-effect for inducing heterogeneous surface charge and consequently changing the fluid flow in a solid-state nanochannel with converging-diverging periodicity. It is shown that the combination of geometry and applied gate voltage (VG) would generate heterogeneous surface charge at the channel walls which can be modulated by VG, i.e. a moderate VG (0.7-0.9 V) causes charge inversion in diverging sections of the channel (Dmax) while VG > 0.9 enables charge inversion in the entire channel but it is still non-uniform in each section. The results show that zeta (ζ) potential is a function of VG which shows a linear to non-linear transition due to dilution of electrolyte in agreement with density functional theory and Monte Carlo simulations. In contrast, electrolyte symmetry has a minor effect on the variation of ζ potential. It is also shown that the difference in ζ potential across the channel (Δζ) increases by dilution of electrolyte and utilizing a more symmetric electrolyte with lower valances. For the first time, it is shown that Δζ presents a maximum with the VG. The VG corresponding to the maximum Δζ decreases with both dilution of electrolyte and higher anion valance. This is of practical importance to overcome leakage current problem of field-effect fluidic devices. It is also shown that the velocity field can be altered by changing both electrolyte concentration and symmetry. However, applying VG was found to be a more efficient way than electrolyte modifications. This includes generating circulation inside the channel which is of prime importance for applications such as mixing or separation/trapping

Application of SiGe(C) in high performance MOSFETs and infrared detectors

Epitaxially grown SiGe(C) materials have a great importance for many device applications. In these applications, (strained or relaxed) SiGe(C) layers are grown either selectively on the active areas, or on the entire wafer. Epitaxy is a sensitive step in the device processing and choosing an appropriate thermal budget is crucial to avoid the dopant out–diffusion and strain relaxation. Strain is important for bandgap engineering in (SiGe/Si) heterostructures, and to increase the mobility of the carriers. An example for the latter application is implementing SiGe as the biaxially strained channel layer or in recessed source/drain (S/D) of pMOSFETs. For this case, SiGe is grown selectively in recessed S/D regions where the Si channel region experiences uniaxial strain.The main focus of this Ph.D. thesis is on developing the first empirical model for selective epitaxial growth of SiGe using SiH2Cl2, GeH4 and HCl precursors in a reduced pressure chemical vapor deposition (RPCVD) reactor. The model describes the growth kinetics and considers the contribution of each gas precursor in the gas–phase and surface reactions. In this way, the growth rate and Ge content of the SiGe layers grown on the patterned substrates can be calculated. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for the diffusion of gas molecules through gas boundaries. Fick‟s law and the Langmuir isotherm theory (in non–equilibrium case) have been applied to estimate the real flow of impinging molecules. For a patterned substrate, the interactions between the chips were calculated using an established interaction theory. Overall, a good agreement between this model and the experimental data has been presented. This work provides, for the first time, a guideline for chip manufacturers who are implementing SiGe layers in the devices.The other focus of this thesis is to implement SiGe layers or dots as a thermistor material to detect infrared radiation. The result provides a fundamental understanding of noise sources and thermal response of SiGe/Si multilayer structures. Temperature coefficient of resistance (TCR) and noise voltage have been measured for different detector prototypes in terms of pixel size and multilayer designs. The performance of such structures was studied and optimized as a function of quantum well and Si barrier thickness (or dot size), number of periods in the SiGe/Si stack, Ge content and contact resistance. Both electrical and thermal responses of such detectors were sensitive to the quality of the epitaxial layers which was evaluated by the interfacial roughness and strain amount. The strain in SiGe material was carefully controlled in the meta–stable region by implementingivcarbon in multi quantum wells (MQWs) of SiGe(C)/Si(C). A state of the art thermistor material with TCR of 4.5 %/K for 100×100 μm2 pixel area and low noise constant (K1/f) value of 4.4×10-15 is presented. The outstanding performance of these devices is due to Ni silicide contacts, smooth interfaces, and high quality of multi quantum wells (MQWs) containing high Ge content.The novel idea of generating local strain using Ge multi quantum dots structures has also been studied. Ge dots were deposited at different growth temperatures in order to tune the intermixing of Si into Ge. The structures demonstrated a noise constant of 2×10-9 and TCR of 3.44%/K for pixel area of 70×70 μm2. These structures displayed an improvement in the TCR value compared to quantum well structures; however, strain relaxation and unevenness of the multi layer structures caused low signal–to–noise ratio. In this thesis, the physical importance of different design parameters of IR detectors has been quantified by using a statistical analysis. The factorial method has been applied to evaluate design parameters for IR detection improvements. Among design parameters, increasing the Ge content of SiGe quantum wells has the most significant effect on the measured TCR value.QC 2011040

Photoacoustic based evaluation of viscoelastic properties of Gram-negative and Gram-positive bacterial colonies

Abstract Mechanical properties of bacterial colonies are crucial considering both addressing their pathogenic effects and exploring their potential applications. Viscoelasticity is a key mechanical property with major impacts on the cell shapes and functions, which reflects the information about the cell envelope constituents. Hereby, we have proposed the application of photoacoustic viscoelasticity (PAVE) for studying the rheological properties of bacterial colonies. In this regard, we employed an intensity-modulated laser beam as the excitation source followed by the phase delay measurement between the generated PA signal and the reference for the characterization of colonies of two different types of Gram-positive and Gram-negative bacteria. The results of our study show that the colony of Staphylococcus aureus as Gram-positive bacteria has a significantly higher viscoelasticity ratio compared to that value for Acinetobacter baumannii as Gram-negative bacteria (77% difference). This may be due to the differing cell envelope structure between the two species, but we cannot rule out effects of biofilm formation in the colonies. Furthermore, a lumped model has been provided for the mechanical properties of bacterial colonies