A three-pronged approach has been used to design rational improvements in self-assembled monolayer field-effect transistors: classical molecular dynamics (MD) simulations to investigate atomistic structure, large-scale quantum mechanical (QM) calculations for electronic properties, and device fabrication and characterization as the ultimate goal. The MD simulations reveal the effect of using two-component monolayers to achieve intact dielectric insulating layers and a well-defined semiconductor channel. The QM calculations identify improved conduction paths in the monolayers that consist of an optimum mixing ratio of the components. These results have been used both to confirm the predictions of the calculations and to optimize real devices. Monolayers were characterized with X-ray reflectivity measurements and by electronic characterization of complete devices.

A combination of in situ vibrational sum-frequency generation (SFG) spectroscopy and molecular-dynamics (MD) simulations has allowed us to study the effects of indentation of self-assembled octadecylphosphonic acid (ODPA) monolayers on α-Al2O3(0001). Stress-induced changes in the vibrational signatures of C-H stretching vibrations in SFG spectra and the results of MD simulations provide clear evidence for an increase in gauche-defect density in the monolayer as a response to indentation. A stress-dependent analysis indicates that the defect density reaches saturation at approximately 155 MPa. After stress is released, the MD simulations show an almost instantaneous healing of pressure-induced defects in good agreement with experimental results. The lateral extent of the contact areas was studied with colocalized SFG spectroscopy and compared to theoretical predictions for pressure gradients from Hertzian contact theory. SFG experiments reveal a gradual increase in gauche-defect density with pressure before saturation close to the contact center. Furthermore, our MD simulations show a spatial anisotropy of pressure-induced effects within ODPA domains: molecules tilted in the direction of the pressure gradient increase in tilt angle while those on the opposite side form gauche-defects.

No abstract

No abstract

We outline an unprejudiced molecular dynamics simulation approach to study the mechanisms of self-organization encompassing the evolution of surfactant-surface interactions to the growth of self-assembled monolayers (SAMs). Therein, the time-length scale problem is tackled by combining an efficient docking-type procedure for implementing surfactant-by-surfactant association with detailed molecular simulations to explore structural relaxation. For this, nanosecond-scale molecular dynamics simulations unravel ordering processes during the gradual assembly of the monolayer. Along this line, different packing motifs of octadecyl phosphonic acid (ODPA) on the (0001) surface of α-alumina and implications for the final density and ordering of the resulting monolayers are elucidated. Moreover, the role of the solvent is discriminated by comparing SAM formation in 2-propanol, hexane and in a vacuum.

135Als Beispiel bringen wir die Umlagerung in Aceton bei 40'. 1 umgelagert Zeit Taupu2kt C,H,Oz (132.2) Ber. C 63,60 11 12,20 Gef. ,, 63,58 ,, 11,78. p-iVitrdenzwt. Aus verd. Methanol fast farblose, rhoinbische Blattchrn v o w Schiiiji. 59". Vcrpufft iii der Flarnme. (!14111108N (281,3) Ber. C 59.77 €I 6,81 Gef. ,, G0,20 ,, 7,15. Darstellung und Veresterung tertiarer H ydroperoxyde 1,1,2,2-TetramethydiithyZhydroperoxyd (CHJa CH -C (CHJa OOH Am 3.3 g Dimethyl-isopropyl-carbinol imd 10 ccm 78proz. H,O,. Die Haul&menge siedete bei 12 mm von 61-48", zeigte starken Poroxydgeruch nnd enthielt nach der Titration 72pror. Peroxyd. Bildet ein Natriumsalz, aus dem das Poroxyd regeaerierbar. Das p-Nitrdenzocit lie0 sich nur gewinnen, wenn sehr schnell gearbeitet wurdr und alle Operationen bei 0" ausgefiihrt wurden. Aus wenig Methanol schied es sich . in schoqen, fast farblosen Blattchen ab. Schinp. 57-68"; verpufft in der Flamme. 139 C131-Il,0,J (267,3) Ber. C 68,41 €I 6,41 Gef. ,, 5827 ,, 6,56. PentamethyZ-uithyZhydro(peroxy~ (CH3),C . C (CH,), OOH Ans 8 g Dimethyl-tert.buty1-carbinol, 40 g 90proz. H,O, und 0,2 ccrn konz. Schwefelsaure unter kraftigem Turbinieren. Nach acht Stunden wurde das festr Reaktionsprodukt abgesaugt, mit Wasser gewaschen, getrocknet, au9 wenig Petrolsther u t e r Verwendung von Eis umkristallisiert und schlieOlich i. V. sublimiert. Campherahnliche Masse vou starkem Peroxydgeruch und groBer Fliichtigkeit.

No abstract

No abstract