Bit patterned media (BPM) have received increased attention in recent years as the primary candidate for 1 Terabit/in2 or higher recording density. A patterned media consists of an array of well-defined magnetic nanostructures, each of which can store one bit of data. In the simplest scheme, the structures could be magnetic pillars and dots with a single easy axis of magnetization. The direction of magnetization is interpreted as a binary 1 or 0. Some of the main technical issues in the BPM include the difficulty in fabricating small nano-island arrays in a periodic fashion over large areas, reliability /reproducibility of magnetic bit characteristics, wear and head flyability issue which is associated with the media surface roughness, and processing cost. This thesis deals with investigation of various fabrication approaches, nanostructural features, and magnetic properties for the bit patterned media. In Chapter 1, the science and technology of patterned magnetic recording media are discussed. In Chapter 2, fabrication of an array of high- coercivity magnetic Co/Pd multilayered islands using pre- patterned Si nanopillars template is described. The Si nanopillars have been prepared by advanced electron beam lithography (EBL) and reactive ion etching (RIE). In Chapter 3, the flying instability of the read/write recording head-slider on the topographically rough surfaces of the nano-patterned media is discussed, and technical approaches to overcome such a problem is described, such as planarization of nanopatterned topography by refilling the trenches and flatten the surface of the BPM. I have investigated the head flyability on BPM by fabricating nano pillar geometry with different topography. For flyability testing that requires a relatively large area, I have also fabricated nano pillars on 2.5 inch glass disks with a distribution of pillar size and periodicity using the "silver ball-up process" and RIE. The process, structure and properties of planarized vs. non-planarized nano fabricated and imprinted BPM, are described in Chapter 4. A Si substrate was spin-coated with a thin PMMA layer, and a periodic island array was made by nano-imprinting lithography (NIL) with the patterned nanofeatures. The subsequent pattern transfer to the Si substrate was performed by using RIE process. A Co/Pd multilayer film was sputtered on the pre- patterned substrate. A HSQ layer was first spin coated on the patterned media to fill the trenches and subsequently re-etched by RIE to remove the overfilled regions on the substrate for planarization. In Chapter 5, the effect of magnetic island geometry on switching field distribution is discussed

Highly sensitive hydrogen detection at room temperature can be realized by employing solution-processed MoS₂ nanosheet-Pd nanoparticle composite. A MoS₂-Pd composite exhibits greater sensing performance than its graphene counterpart, indicating that solvent exfoliated MoS₂ holds great promise for inexpensive and scalable fabrication of highly sensitive chemical sensors.

A zeolitic 4A type material was successfully prepared from natural basalt rock by applying an alkali fusion process and hydrothermal synthesis. In particular, the optimum synthetic conditions were examined at different crystallization times. Several methods such as XRD, SEM, EDX, and N₂ and CO₂ adsorption analysis were used to characterize the synthesized 4A type zeolite. In addition, CO₂ adsorption equilibrium capacities for this basalt base zeolite were measured over temperature ranges from 283 to 303 K and pressure ranges from 0.1 to 1500 kPa in a volumetric adsorption apparatus. Then the results were compared to those of commercial zeolite. Moreover, to further investigate the surface energetic heterogeneity of the prepared zeolite, the isosteric heat of adsorption and adsorption energy distribution was determined. We found that basalt based zeolite 4A shows a CO₂ adsorption equilibrium capacity of 5.9 mmol g^-1 (at 293 K and 1500 kPa) which is much higher than the 3.6 mmol g^-1 of the commercial zeolite as its micro-pore surface area, micro-pore volume and surface heterogeneity indicate.

For nearly 50 years, the vision of using single molecules in circuits has been seen as providing the ultimate miniaturization of electronic chips. An advanced example of such a molecular electronics chip is presented here, with the important distinction that the molecular circuit elements play the role of general-purpose single-molecule sensors. The device consists of a semiconductor chip with a scalable array architecture. Each array element contains a synthetic molecular wire assembled to span nanoelectrodes in a current monitoring circuit. A central conjugation site is used to attach a single probe molecule that defines the target of the sensor. The chip digitizes the resulting picoamp-scale current-versus-time readout from each sensor element of the array at a rate of 1,000 frames per second. This provides detailed electrical signatures of the single-molecule interactions between the probe and targets present in a solution-phase test sample. This platform is used to measure the interaction kinetics of single molecules, without the use of labels, in a massively parallel fashion. To demonstrate broad applicability, examples are shown for probe molecule binding, including DNA oligos, aptamers, antibodies, and antigens, and the activity of enzymes relevant to diagnostics and sequencing, including a CRISPR/Cas enzyme binding a target DNA, and a DNA polymerase enzyme incorporating nucleotides as it copies a DNA template. All of these applications are accomplished with high sensitivity and resolution, on a manufacturable, scalable, all-electronic semiconductor chip device, thereby bringing the power of modern chips to these diverse areas of biosensing.