Jean ISDRS 2007
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1. The document discusses metal-molecule-GaAs devices using self-assembled monolayers of redox-active molecules. 2. Three molecules - octadecanethiol, a ligand, and a ruthenium complex - were deposited on GaAs and tested. 3. Current-voltage measurements showed higher current densities in the molecular devices compared to a control metal-semiconductor device, and thermionic and thermionic-field emission models were found to fit the data.
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Cobalt ferrite (CoFe2O4), an inverse spinal ferrite has high permeability, good saturation 1magnetization and no preferred direction of magnetization, high Curie temperature, and high electromagnetic performance. In the present work 0.2M cobalt nitrate 0.3M ferric nitrate and 0.4 M citric acid is used to synthesis cobalt ferrite nanoparticle by sol-gel technique. As the magnetic property depends on the grain size of the synthesized nanoparticle, metal nitrate to citric acid ratio is varied from 0.8, 0.6 and 0.4 and the structural, functional morphological and magnetic characteristics are analyzed. The structural analysis shows the decrease in the average crystallite from 37 to 27nm when CAMN ratio decreases from 0.8 to 0.4. The strain is directly proportional to dislocation density and it reflects the growth of the average grain size, and in the present study, it reflects the same. The calculated lattice parameter is found to be close to 8.373 Ã… and the volume of the cell is found to be 5.63x10-28 m is close to the standard value for the cobalt ferrite nanoparticles. From the EDS spectrum, the presence of Co, Fe, and O in the synthesized nanoparticles are noted. Functional groups analysis by FTIR shows the presence of organic sources. Surface morphology by Scanning electron microscope shows the distribution of spherical sized nanoparticles agglomerated in different sizes and the grain size calculated by image J software are close to the calculated value by Scherrer formula from XRD. Chitra | T Raguram | K S Rajni"Microstructural and Magnetic Properties of Cobalt Ferrite Nanoparticles Synthesized by Sol-Gel Technique" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: http://www.ijtsrd.com/papers/ijtsrd15871.pdf http://www.ijtsrd.com/physics/other/15871/microstructural-and-magnetic-properties-of-cobalt-ferrite-nanoparticles-synthesized-by-sol-gel-technique/chitra
Kazarinov
This document summarizes spectroscopic studies of defects in gamma- and neutron-irradiated magnesium aluminate spinel ceramics. It discusses how irradiation induces optical centers in the UV-Vis and IR spectra. Electron paramagnetic resonance (EPR) spectroscopy and radioluminescence were also used to characterize defects. Two stages of annealing were observed, with cation defects recombining at lower temperatures followed by anion defects at higher temperatures. The document provides experimental details on sample preparation, irradiation sources and doses, and investigation methods used.
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Jean ISDRS 2007
- 1. Metal-Molecule-GaAs Devices Using Redox-Active Self Assembled Monolayers 2007 ISDRS a Rand Jean, b Bin Xi, b Tong Ren and a David B. Janes a School of Electrical & Computer Engineering, Purdue University b Department of Chemistry, Purdue University
- 4. 2007 ISDRS Device Fabrication 3 1. GaAs with ohmic back contact 2. SiO2 deposition and patterning 3. Molecular deposition 4. Au deposition and patterning Final measured structures Low energy, non destructive deposition of Au
- 8. 2007 ISDRS 7 Ren et. al. J Orgn. Chem. 690, 4734, 2005. Energies of Molecular Levels (C-V) Cyclic voltammogram of Ru molecule E f(Au) = 5.1 0.13 0.5 5.23 4.6 GV Analysis E vac Energy ( eV ) 0.13 0.5 4.97 5.6 E NHE = 4.43 E Ag / AgCl = 0.197 + - CV 0 ~ 4.63 0.4 0.4 2.0 5.0 4.2 2 .6 CV Analysis E HOMO E LUMO (1) E LUMO (2) E mol Au E F
- 10. 2007 ISDRS Proposed Model 9 Metal Semiconductor Metal Semiconductor Molecule TFE TE TFE ODT Ligand Ru Ev Ef Ec Thermionic Emission Thermionic Field Emission φ 1 φ 2 Φ 1 > Φ 2
- 11. 2007 ISDRS 10 Thermionic &Thermionic-Field Emission comparison
- 12. 2007 ISDRS Thermionic &Thermionic-Field Emission comparison Cont’d 11
- 13. Thermionic &Thermionic-Field Emission comparison Cont’d 2007 ISDRS 12
Editor's Notes
- This summarizes investigations into the current-voltage characteristics of certain classes of organic molecules with emphasis on Ruthenium complex redox-active molecules.
- Summary of main points:
- What are MMS structures: Explain diagram on top left What are redox-active devices: Explain diagram on top middle and bottom Why are they important: Explain Top right.
- n+doped (2e18 cm^-3) GaAs single side polished with Au/Ti/Au/Ge/Ni at 4000/1000/2500/300/130 Å respectively ohmic back contact. S1805 light PR deposited and patterned. SiO2 deposition (1000Å). Lift-off by soaking in acetone overnight and 1.5 minutes in O2 atm in RIE to remove remnant PR epilayer. Molecular Deposition by soaking in solution of molecule for 24 hours. Solvent Cleaning to remove phys-absorbed molecules from the surface; 20 ultrasonication in the solvent (ethanol or tetrahydrofuran).
- Left: time of flight sims shows that Ar backfill when compared to other meathods have the least amount of metal penetration in the mol layer. Right: IV show that greater current density in mol layer with Ar backfill.
- All molecules deposited are asymmetric with dipole moments. ODT is a simple alkanethiol used frequently in SAMs with well known surface density properties and electrical characteristics, ie. leaky dielectric. It Has great surface coverage and thus we expect unpinning of Ef in GaAs which occurs when surface states are about 5e13 states/cm2/eV Ru complex family of molecules were designed to be a ‘molecular wires’ with energy levels accessible using modest biases (E-levels from 0.67-1.29 V). It has horrible surface coverage, so we should expect surface pinning, of Ef Ligand is short aromatic molecule initially used to prop up the larger bulkier Ru complex in a matrix. However the delocalized electron cloud around the benzene is suspected to Contribute in current conduction. Might be surface unpinning…..don;t know the coverage data on such mol
- Mixed Monolayer matrix. STM image and height of Ru complex above C11 matrix. In this experiment, the Ligand was used due to the similarity of the base of Ru complex to Ligand molecule. There might be surface unpinning due to coverage of both mol
- Most conductive is the Ru complex; least conductive is the control by 4 orders of magnitude. At 1 V the ODT and Mixed Monolayer are about the same conductivity, Followed by the Ligand and lastly the control.
- Initial understanding follows: Mol layer with lower dielectric constant has more voltage dropped across it Q/V = Ae/t as a result barrier hieght is reduced and TFE is encouraged. Ru complex shows different pattern, its horrendous coverage should not allow for much potential drop across it. Also ligand is shortest mol and coverage is better than Ru, direct tunneling is not the main explanation. However E-level assisted tunneling does explain.
- IV over range which excludes non ideal effects such as series resistance Recombination in first 0.1V can explain deviation from theory General agreement to theory TFE and TE is possible explanation and E-level assisted TFE in case of Ru
- Follows theory
- Mixed mono and ODT show least RG, possibility exist that good surface coverage of those mol could be removing dangling bonds which cause surface states
- Summary of theory and parameters High values of n indicates high recombination current and other non idealities. This could indicate the horrible surface coverage of the individual ligand and Ru complexes
- ODT is taken as example for non redox active mol Ru is redox active example.