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- Title
- CONTROLLED DEPOSITION OF MAGNETIC MOLECULES AND NANOPARTICLES ON ATOMICALLY FLAT GOLD SURFACES.
- Creator
-
Haque, Md. Firoze, del Barco, Enrique, University of Central Florida
- Abstract / Description
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In this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters...
Show moreIn this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters and conditions necessary to deposit a monolayer of nano-substance on chips containing gold nanowires which will eventually be used to form single electron transistors by electromigration breaking of the nanowire. Maximization of the covered surface area is crucial to optimize the yield of finding a molecule/nanoparticle near the gap formed in the nanowire after electromigration breaking. Coverage of the surface by molecules/nanoparticles mainly depends on the deposition time and concentration of the solution used for the self-assembly. Deposition of the samples under study was done for different solution concentrations and deposition times until a self-assembly monolayer covering most of the surface area is obtained. Imaging of the surfaces after deposition was done by tapping-mode AFM. Analysis of the AFM images was performed and deposition parameters (i.e. coverage or molecule/particle size distribution) were obtained. The subjects of this investigation were a molecular polyoxometalate, a single-molecule magnet and functionalized gold nanoparticles. The obtained results agree with the structure of each of the studied systems. Using the optimized deposition parameters found in this investigation, single-electron transport measurements have been carried out. Preliminary results indicate the right choice of the deposition parameters.
Show less - Date Issued
- 2008
- Identifier
- CFE0002338, ucf:47795
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002338
- Title
- SINGLE-ELECTRON TRANSPORT SPECTROSCOPY STUDIES OF MAGNETIC MOLECULES AND NANOPARTICLES.
- Creator
-
Haque, Md. Firoze, del Barco, Enrique, University of Central Florida
- Abstract / Description
-
Magnetic nanoparticles and molecules, in particular ferromagnetic noble metal nanoparticles, molecular magnet and single-molecule magnets (SMM), are perfect examples to investigate the role of quantum mechanics at the nanoscale. For example, SMMs are known to reverse their magnetization by quantum tunneling in the absence of thermal excitation and show a number of fundamental quantum mechanical manifestations, such as quantum interference effects. On the other hand, noble metal nanoparticles...
Show moreMagnetic nanoparticles and molecules, in particular ferromagnetic noble metal nanoparticles, molecular magnet and single-molecule magnets (SMM), are perfect examples to investigate the role of quantum mechanics at the nanoscale. For example, SMMs are known to reverse their magnetization by quantum tunneling in the absence of thermal excitation and show a number of fundamental quantum mechanical manifestations, such as quantum interference effects. On the other hand, noble metal nanoparticles are found to behave ferromagnetically for diameters below a few nanometers. Some of these manifestations are still intriguing, and novel research approaches are necessary to advance towards a more complete understanding of these exciting nanoscale systems. In particular, the ability to study an isolated individual nanoscale system (i.e just one molecule or nanoparticle) is both challenging technologically and fundamentally essential. It is expected that accessing to the energy landscape of an isolated molecule/nanoparticle will allow unprecedented knowledge of the basic properties that are usually masked by collective phenomena when the systems are found in large ensembles or in their crystal form. Several approaches to this problem are currently under development by a number of research groups. For instance, some groups are developing deposition techniques to create patterned thin films of isolated magnetic nanoparticles and molecular magnets by means of optical lithography, low-energy laser ablation, or pulsed-laser evaporation or specific chemical functionalization of metallic surfaces with special molecular ligands. However, it is still a challenge to access the properties of an individual molecule or nanoparticle within a film or substrate. I have studied molecular nanomagnets and ferromagnetic noble metal nanoparticles by means of a novel experimental approach that mixes the chemical functionalization of nano-systems with the use of single-electron transistors (SETs). I have observed the Coulomb-blockade single-electron transport response through magnetic gold nanoparticles and single-molecule magnet. In particular, Coulomb-blockade response of a Mn4-based SET device recorded at 240 mK revealed the appearance of two diamonds (two charge states) with a clear switch between one and the other is indicative of a conformational switching of the molecule between two different states. The excitations inside the diamonds move with magnetic field. The curvature of the excitations and the fact of having them not going down to zero energy for zero magnetic field, indicated the presence of magnetic anisotropy (zero-field splitting) in the molecule. In addition, the high magnetic field slope of the excitations indicates that transitions between charge states differ by a net spin value equal to 9 (dS = 9), as expected from the behavior of Mn4 molecules in their crystalline form. Anticrossings between different excitations are indicative of quantum superpositions of the molecular states, which are observed for the first time in transport measurements through and individual SMM.
Show less - Date Issued
- 2011
- Identifier
- CFE0003718, ucf:48776
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003718
