A New Route to Prepare Hard and Anti-Scratching Coatings at Room Temperature

1999 ◽  
Vol 576 ◽  
Author(s):  
Yanjing Liu ◽  
Richard O. Claus ◽  
Aprillya Rosidian ◽  
Tingying Zeng
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Crystal Silicon ◽  
Linear Behavior ◽  
Vis Spectroscopy ◽  
Novel Method ◽  
Quartz Substrates ◽  
Cationic Polyelectrolytes

ABSTRACTNanocomposites of transparent, multilayer structures of different thin-films have been fabricated on single crystal silicon and quartz substrates by the new deposition technique called electrostatic self-assembly (ESA) method. The method is based on the alternating adsorption of anionic and cationic polyelectrolytes in the aqueous forms. The films were then characterized by UV/Vis spectroscopy, ellipsometry, and nano-indenter. A linear behavior of both optical absorption and film thickness as the number of bilayers increases was observed, which indicated the formation of homogeneous and uniform thin-films on both substrates. The study also observed that the films prepared by this novel method have some improved mechanical properties.

Giant Magnetoresistance of Electrostatic Self-Assembled Fe3O4 Nanocluster and Polymer Thin-Films

1999 ◽  
Vol 577 ◽  
Author(s):  
Yanjing Liu ◽  
Richard O. Claus ◽  
Fajian Zhang
Keyword(s):  
Aqueous Solution ◽  
Self Assembly ◽  
Giant Magnetoresistance ◽  
Single Crystal Silicon ◽  
Crystal Silicon ◽  
Angle Measurements ◽  
Vis Spectroscopy ◽  
Contact Angle Measurements ◽  
Assembly Technique ◽  
Quartz Substrates

ABSTRACTGiant magnetoresistance (GMR) as large as 25% at 25°C has been observed for multilayer ultrathin films of iron oxide (Fe3O4) nanoclusters and polyimide molecules alternately adsorbed onto single crystal silicon and quartz substrates using a novel self-assembly technique. This process involves the alternate dipping of a substrate into an aqueous solution of anionic polyimide precursor (polyamic salt, PAA) followed by dipping it into an aqueous solution of cationic polydiallyldimethylammonium chloride (PDDA)-coated Fe3O4, nanoparticles. The regular formation of alternating monolayers is verified by UV-vis spectroscopy and contact angle measurements. Vibrating sample magnetometry indicates the formation of ultrasoft films.

Molecular Self-Assembly of Fe3O4/Polyimide Nanocomposite Films (I)

1997 ◽  
Vol 475 ◽  
Author(s):  
Yanjing Liu ◽  
Anbo Wang ◽  
Richard O. Claus ◽  
Eric Jiang
Keyword(s):  
Aqueous Solution ◽  
Self Assembly ◽  
Single Crystal Silicon ◽  
Magnetic Films ◽  
Nanocomposite Films ◽  
Layer By Layer ◽  
Crystal Silicon ◽  
Vis Spectroscopy ◽  
Polyimide Nanocomposite ◽  
Polyimide Precursor

ABSTRACTLayer-by-layer molecular self-assembly of nanosized magnetite (Fe3O4) particles and polyimide precursor molecules into multilayer ultrathin films has been accomplished on single crystal silicon and quartz substrates. This process involves the alternate dipping of a substrate into an aqueous solution of cationic polymer which coats on nanoscale Fe3O4 particles as a stabilizer followed by dipping into an aqueous solution of anionie polyimide precursor (polyamic acid salt, PAATEA). The growth process and the structure have been characterized using UV-vis spectroscopy, FT-IR, and scanning electron microscopy. The results demonstrate that well-ordered uniform monolayer and multilayer magnetic films have been formed on silicon and silica surfaces.

HREM observation of dislocations near room temperature fractures in silicon

1988 ◽  
Vol 46 ◽  
pp. 892-893
Author(s):  
M. H. Rhee ◽  
W. A. Coghlan
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Dislocation Nucleation ◽  
Back Side ◽  
Ion Milling ◽  
Crystal Silicon ◽  
Flat Surfaces ◽  
Induced Fractures ◽  
Vicker’S Microhardness

Silicon is believed to be an almost perfectly brittle material with cleavage occurring on {111} planes. In such a material at room temperature cleavage is expected to occur prior to any dislocation nucleation. This behavior suggests that cleavage fracture may be used to produce usable flat surfaces. Attempts to show this have failed. Such fractures produced in semiconductor silicon tend to occur on planes of variable orientation resulting in surfaces with a poor surface finish. In order to learn more about the mechanisms involved in fracture of silicon we began a HREM study of hardness indent induced fractures in thin samples of oxidized silicon.Samples of single crystal silicon were oxidized in air for 100 hours at 1000°C. Two pieces of this material were glued together and 500 μm thick cross-section samples were cut from the combined piece. The cross-section samples were indented using a Vicker's microhardness tester to produce cracks. The cracks in the samples were preserved by thinning from the back side using a combination of mechanical grinding and ion milling.

Green synthesis of mixed metallic nanoparticles using room temperature self-assembly

2017 ◽  
Vol 13 (2) ◽  
pp. 4671-4677 ◽  
Author(s):  
A. M. Abdelghany ◽  
A.H. Oraby ◽  
Awatif A Hindi ◽  
Doaa M El-Nagar ◽  
Fathia S Alhakami
Keyword(s):  
Self Assembly ◽  
Metallic Nanoparticles ◽  
Room Temperature ◽  
Bimetallic Nanoparticles ◽  
Reduction Process ◽  
Nano Particles ◽  
Nano Structure ◽  
Small Shift ◽  
Molar Ratios ◽  
Vis Spectroscopy

Bimetallic nanoparticles of silver (Ag) and gold (Au) were synthesized at room temperature using Curcumin. Reduction process of silver and gold ions with different molar ratios leads to production of different nanostructures including alloys and core-shells. Produced nanoparticles were characterized simultaneously with FTIR, UV/vis. spectroscopy, transmission electron microscopy (TEM), and Energy-dispersive X-ray (EDAX). UV/vis. optical absorption spectra of as synthesized nanoparticles reveals presence of surface palsmon resonance (SPR) of both silver at (425 nm) and gold at (540 nm) with small shift and broadness of gold band after mixing with resucing and capping agent in natural extract which suggest presence of bimetallic nano structure (Au/Ag). FTIR and EDAX data approve the presence of bimetallic nano structure combined with curcumin extract. TEM micrographs shows that silver and gold can be synthesized separately in the form of nano particles using curcumin extract. Synthesis of gold nano particles in presence of silver effectively enhance and control formation of bi-metallic structure.

Silicon Carbide Die Attach Scheme for 500°C Operation

2000 ◽  
Vol 622 ◽  
Author(s):  
Liang-Yu Chen ◽  
Gary W. Hunter ◽  
Philip G. Neudeck
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Semiconductor Devices ◽  
Single Crystal Silicon ◽  
Film Material ◽  
Crystal Silicon ◽  
Pure Alumina ◽  
Die Attach

ABSTRACTSingle crystal silicon carbide (SiC) has such excellent physical, chemical, and electronic properties that SiC based semiconductor electronics can operate at temperatures in excess of 600°C well beyond the high temperature limit for Si based semiconductor devices. SiC semiconductor devices have been demonstrated to be operable at temperatures as high as 600°C, but only in a probe-station environment partially because suitable packaging technology for high temperature (500°C and beyond) devices is still in development. One of the core technologies necessary for high temperature electronic packaging is semiconductor die-attach with low and stable electrical resistance. This paper discusses a low resistance die-attach method and the results of testing carried out at both room temperature and 500°C in air. A 1 mm2 SiC Schottky diode die was attached to aluminum nitride (AlN) and 96% pure alumina ceramic substrates using precious metal based thick-film material. The attached test die using this scheme survived both electronically and mechanically performance and stability tests at 500°C in oxidizing environment of air for 550 hours. The upper limit of electrical resistance of the die-attach interface estimated by forward I-V curves of an attached diode before and during heat treatment indicated stable and low attach-resistance at both room-temperature and 500°C over the entire 550 hours test period. The future durability tests are also discussed.

The Use of Energy Dispersive Diffractometry to Measure the Thickness of Metal and Glass Thin Films

1981 ◽  
Vol 25 ◽  
pp. 365-371
Author(s):  
Glen A. Stone
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Single Crystal Silicon ◽  
Substrate Material ◽  
Silicon Wafers ◽  
Energy Dispersive ◽  
Crystal Silicon ◽  
X Ray ◽  
Phosphosilicate Glass ◽  
Film Substrate

This paper presents a new method to measure the thickness of very thin films on a substrate material using energy dispersive x-ray diffractometry. The method can be used for many film-substrate combinations. The specific application to be presented is the measurement of phosphosilicate glass films on single crystal silicon wafers.

Selective and low temperature synthesis of polycrystalline diamond

1991 ◽  
Vol 6 (6) ◽  
pp. 1278-1286 ◽  
Author(s):  
R. Ramesham ◽  
T. Roppel ◽  
C. Ellis ◽  
D.A. Jaworske ◽  
W. Baugh
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Substrate Temperature ◽  
Microwave Plasma ◽  
Diamond Particle ◽  
Single Crystal Silicon ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Crystal Silicon ◽  
Diamond Thin Films

Polycrystalline diamond thin films have been deposited on single crystal silicon substrates at low temperatures (⋚ 600 °C) using a mixture of hydrogen and methane gases by high pressure microwave plasma-assisted chemical vapor deposition. Low temperature deposition has been achieved by cooling the substrate holder with nitrogen gas. For deposition at reduced substrate temperature, it has been found that nucleation of diamond will not occur unless the methane/hydrogen ratio is increased significantly from its value at higher substrate temperature. Selective deposition of polycrystalline diamond thin films has been achieved at 600 °C. Decrease in the diamond particle size and growth rate and an increase in surface smoothness have been observed with decreasing substrate temperature during the growth of thin films. As-deposited films are identified by Raman spectroscopy, and the morphology is analyzed by scanning electron microscopy.

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