Post-metallization annealing and photolithography effects in p-type Ge/Al2O3/Al MOS structures

In this work, the combined effect of negative tone photolithography and post-metallization annealing (PMA) on the electrical behavior of Al/Al2O3/p-Ge MOS structures are investigated. During photoresist development, the exposed upper part of the Al2O3 film weakens due to the reaction with the developer. Subsequent processes of Al deposition and PMA at 350 °C result in alumina thickness reduction. The gate electrode formation seems to involve at least three processes: (a) germanium substrate out-diffusion and accumulation at the top of the alumina layer that takes place during the alumina deposition, (b) alumina destabilization, and (c) germanium diffusion into the deposited Al metal and Al diffusion into the alumina. The overall effect is the reduction of the alumina thickness due to its partial consumption. It is shown that the germanium diffusion depends on the annealing duration, and not on the annealing ambient (inert or forming gas). Although PMA passivates interface traps near the valence band edge, the insulating properties of the stacks are degraded. This degradation appears as a low-level ac loss, attributed to a hopping current that flows through the Al2O3 layer. The results are discussed and compared to recently reported on Pt/Al2O3/p-Ge structures formed and treated under the same conditions

Molecular junctions made of tungsten-polyoxometalate self-assembled monolayers: Towards polyoxometalate-based molecular electronics devices

In this work, the electrical conduction of planar Au junctions electrically bridged by a polyoxometalate-based self-assembled monolayer, aimed to be used in hybrid silicon/molecular memory devices, is discussed. Tunnelling assisted by the presence of polyoxometalate anions is recognised as the main conduction mechanism for these devices. Fluctuations and hysteresis that are profoundly observed in the current-voltage characteristics for the smallest junctions suggest that the anions number is the more crucial factor in the devices behaviour. Quantitative analysis of the obtained characteristics based on Simmons's model reveals an increase in the tunnelling barrier height as the electrode distance increases from 20 to 200 nm. (C) 2011 Elsevier B.V. All rights reserved

Emergence of ambient temperature ferroelectricity in meso-tetrakis(1- methylpyridinium-4-yl)porphyrin chloride thin films

Here, we demonstrate that the meso-tetrakis(1-methylpyridinium-4-yl) porphyrin chloride, [H2TMPyP]4+Cl4, with a face-to-face orientation directed along a single direction displays ferroelectric properties at room temperature. This is attributed to its spontaneous polarization, due to an extensive hydrogen-bonded network. From C-V measurements, a remnant polarization of approximately 0.5 μC cm-2 was estimated for pristine porphyrin film, which increases linearly up to about 1.7 μC cm-2 after applying 2 V at the top electrode and further to 9.6 μC cm-2 after 5 V positive poling. This large - for practical utilization - level of remnant polarization of [H2TMPyP] 4+Cl4 makes it promising for future applications.</p

Post-metallization annealing and photolithography effects in p-type Ge/Al 2 O 3 /Al MOS structures

In this work, the combined effect of negative tone photolithography and post-metallization annealing (PMA) on the electrical behavior of Al/Al2O3/p-Ge MOS structures are investigated. During photoresist development, the exposed upper part of the Al2O3 film weakens due to the reaction with the developer. Subsequent processes of Al deposition and PMA at 350 °C result in alumina thickness reduction. The gate electrode formation seems to involve at least three processes: (a) germanium substrate out-diffusion and accumulation at the top of the alumina layer that takes place during the alumina deposition, (b) alumina destabilization, and (c) germanium diffusion into the deposited Al metal and Al diffusion into the alumina. The overall effect is the reduction of the alumina thickness due to its partial consumption. It is shown that the germanium diffusion depends on the annealing duration, and not on the annealing ambient (inert or forming gas). Although PMA passivates interface traps near the valence band edge, the insulating properties of the stacks are degraded. This degradation appears as a low-level ac loss, attributed to a hopping current that flows through the Al2O3 layer. The results are discussed and compared to recently reported on Pt/Al2O3/p-Ge structures formed and treated under the same conditions

Issues with n-type Dopants in Germanium

The last decade has seen considerable experimental and theoretical work towards the use of germanium for high-speed low-power electronics. Despite the demonstration of high performance p-channel Ge transistors in planar and non-planar device technology, fabrication of n-channel Ge transistors faces a number of scientific and technological challenges, which hinder the development of CMOS logic circuits based entirely on Ge. Major challenge constitutes the control of fast n-type dopant (out-/in-)diffusion in Ge, which prevents the formation of ultra-shallow and highly activated n+/p junctions necessary for n-channel Ge MOSFET’s enhanced performance. The paper focuses on parameters affecting n-type dopant diffusion in Ge and the attempts to suppress it, with particular emphasis on the action of nitrogen as phosphorous diffusion blocker

Unsymmetrical surface modification of a heteropolyoxotungstate via in-situ generation of monomeric and dimeric copper(II) species

Unsymmetrical functionalization of a discrete &#945;-{SiW&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;40&lt;/sub&gt;} Keggin with two heterometallic building blocks, a Cu(II) dimer and a Cu(II) monomer, results in the formation of [{Cu&lt;sub&gt;2&lt;/sub&gt;(O&lt;sub&gt;2&lt;/sub&gt;CMe)&lt;sub&gt;2&lt;/sub&gt;(5,5'-dimethyl-2,2'-bipy)&lt;sub&gt;2&lt;/sub&gt;}{Cu(5,5'-dimethyl-2,2' -bipy)&lt;sub&gt;2&lt;/sub&gt;}SiW&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;40&lt;/sub&gt;]that displays interesting physical properties