Processing-texture relationships in dual-unbalanced magnetron deposition of TiN films

There has been sustained interest in using TiN and other sputter deposited thin film materials in electronics applications, such as barrier coatings. However, it is difficult to produce “pin-hole free” coatings using conventional magnetron sputtering, since the high bias potentials required to produce dense films often result in substrate damage. “Unbalanced” magnetron sputtering may offer a low energy alternative since the ion-to-deposited-atom ratio can be greatly increased, permitting the ion-bombardment energy to be reduced to <200 eV, without sacrificing film density, hardness, or adhesion. As has been demonstrated previously, ion energy can have a profound effect on film texture, but what affect the “substitution” of ion flux for ion energy will have on film texture has not been determined. In this work, TiN films were deposited onto M2 steel via “unbalanced” magnetron sputtering in an attempt to correlate changes in film texture and film stress, with ion energy and flux.     

Two-electron photo-ionization from deep states in semiconductors

Photo-ionization (P-I) from deep states in semiconductors can be used to explore the band structure of the crystal as well as to give detailed information about the symmetry and other properties of the bound states themselves. When 2 electrons are bound to a defect the P-I spectrum at high photon energy reflects the initial and final state properties of both electrons. Only at low energies, where one electron is transferred into its 1-electron ground state does the P-I process of a 2-electron state resemble that of a 1-electron state. This fact offers a resolution of the two different interpretations of P-I from the 0^- state in GaP as reported by Henry et al. from photo-capacitance studies and by Grimmeiss et al. from photo-conductivity. In the latter the 4 lowest enercry thresholds (E_i = 0.65 to 1.19 eV) correspond to “1-electron” P-I with the 0 center left in its neutral ground state. Only above about 1.4 eV do the “2-electron” processes appear. In photo-capacitance the “2-electron” processes dominate (the “1-electron” thresholds being too weak or too diffuse to be identified), and the spectrum is strongly modified by relaxation of the lattice around the 0⁺ ion.     

EACLE : Energy-Aware Clustering Scheme with Transmission Power Control for Sensor Networks

In this paper, we propose a new energy efficient clustering scheme with transmission power control named “EACLE” (Energy-Aware CLustering scheme with transmission power control for sEnsor networks) for wireless sensor networks, which are composed of the following three components; “EACLE clustering” is a distributed clustering method by means of transmission power control, “EACLE routing” builds a tree rooted at a sink node and sets the paths from sensor nodes taking energy saving into consideration, and “EACLE transmission timing control” changes the transmission timing with different levels of transmission power to avoid packet collisions and facilitates packet binding. With an indoor wireless channel model which we obtained from channel measurement campaigns in rooms and corridors and an energy consumption model which we obtained from a measurement of a chipset, we performed computer simulations to investigate the performance of EACLE in a realistic environment. Our simulation results indicate that EACLE outperforms a conventional scheme such as EAD (Energy-Aware Data-centric routing) in terms of communication success rate and energy consumption. Furthermore, we fully discuss the impact of transmission power and timing control on the performance of EACLE.     

ATM cell encryption and key update synchronization

This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer Mode) cells. The presented approach converts a plaintext into pseudo‐random plaintext before ciphering to conceal patterns in the plaintext. The underlying idea behind this scheme is the Shannon's principles of “confusion” and “diffusion” which involve breaking dependencies and introducing as much randomness as possible into the ciphertext. In this scheme, confusion and diffusion are introduced into the system by first compressing the ATM cell payload and then spreading a continuously changing random data over the entire content of the cell. As a mode of operation for block ciphering, this scheme offers the following attractive features:(i) plaintext patterns are pseudo‐randomized and chained with ciphertext (thereby, preventing against “dictionary”, “known plaintext”, and “statistical analysis” attacks), (ii) it is self‐synchronizing, (iii) cell loss has no additional negative effect, (iv) no IV (Initialization Vector) storage is required, (v) it is encryption‐algorithm independent, (vi) there is no cell‐to‐cell dependency (no feedback from previous cells), and (vii) it is highly scalable (i.e., cells from the same stream can be ciphered and deciphered in parallel). This paper also presents a secure mechanism for in‐band synchronization of encryption/decryption key updates using a “marker‐cell” that is carried within the data channel. An important aspect of both the above mechanisms is that they do not require any changes to the ATM cell header or ATM infrastructure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Routing with off-network control: a novel paradigm for scalable design in very large sensor networks

This paper presents a novel architectural solution to address the problem of scalable routing in very large sensor networks. The control complexities of the existing sensor routing protocols, both flat and with traditional hierarchy, do not scale very well for large networks with potentially hundreds of thousands of embedded sensor devices. This paper develops a novel routing solution Off-Network Control Processing (ONCP) that achieves control scalability in large sensor networks by shifting certain amount of routing functions “off-network”. This routing approach, consisting of “coarse grain” global routing, and distributed “fine grain” local routing is proposed for achieving scalability by avoiding network-wide control message dissemination. We present the ONCP architectural concepts and analytically characterize its performance in relation to both flat and traditional hierarchical sensor routing architectures. We also present ns2-based experimental results which indicate that for very large networks, the packet drop, latency and energy performance of ONCP can be significantly better than those for flat sensor routing protocols such as Directed Diffusion and cluster-based traditional hierarchical protocols such as CBRP.     

Decoupled Power Allocation Through Pricing on a CDMA Reverse Link Shared by Energy-Constrained and Energy-Sufficient Data Terminals

We perform market-oriented management of the reverse link of a CDMA cell populated by data terminals, each with its own data rate, channel gain, willingness to pay (wtp), and link-layer configuration, and with energy supplies that are limited for some, and inexhaustible for others. For both types of energy budgets, appropriate performance indices are specified. Notably, our solution is “decoupled” in that a terminal can choose optimally, irrespective from choices made by the others, because it pays in proportion to its fraction of the total power at the receiver, which directly determines its signal-to-interference ratio (SIR), and hence its performance. By contrast, in other similarly-sounding schemes terminals’ optimal choices are interdependent, which leads to “games of strategy”, and their practical and theoretical complications. We study two situations: pricing for maximal (i) network revenue, and (ii) social benefit. The socially-optimal price is common to all terminals of a given energy class, and an energy-constrained terminal pays in proportion to the square of its power fraction. By contrast, the revenue-maximising network sets for each terminal an individual price that drives the terminal to the “revenue per Watt” maximiser. The network price is higher, and drives each terminal to consume less. Distinguishing features of our model are: (i) the simultaneous consideration of both limited and unlimited energy supplies, (ii) the performance metrics utilised (one for each type of energy supply), (iii) the generality of our physical model, which can lead to an optimal link-layer configuration, and (iv) our pricing of the received power fraction which yields a “decoupled” solution.     

Polarization echoes in piezoelectric semiconductors

In many piezoelectric crystals, application of a se-quence of two or three microwave electric field pulses creates a polarization which radiates subsequent “echo” signals (analogous to spin echoes). Two distinct types of echo phenomena may be delineated. Both involve a nonlinear interaction of a forward propagating acoustic wave (ω,k) (launched by the first microwave pulse (ω,0), with the uniform microwave electric field of the second pulse (ω,0) . The nonlinearities are derivable on the basis of field induced ionization of electrons from shallow impurity states (traps). The first echo phenomenon, which we term “parametric echo”, is a backward wave parametric process. The pump being provided by the 2ω component of the conduction band electron density resulting from ionization by an ω electric field. In the second phenomenon, “holographic echo”, electrons are transferred among the traps to create a static charge distribution which is a stored hologram representing the interference pattern (with wave vectork) of the acoustic and electric fields. At low temperatures (4.2°K) in CdS, CdSe, and CdTe the pattern is stable in the dark for months. A third (or any subsequent) pulse, (ω,0) or (ω,k), produces an output echo (ω,k) or (ω,0), respectively, through electrostriction. Under illumination by low level white light the variation of echo amplitude with microwave power involves the energy distribution of the trap levels, and the latter may be obtained from the data. Results for a fully compensated CdS:S sample are presented.     

Robust Continuous-Time Matrix Estimation under Dependent Noise Perturbations: Sliding Modes Filtering and LSM with Forgetting

This paper deals with time-varying parameter estimation of stochastic systems under dependent noise perturbations. The filter, which generates this dependent noise from a standard “white noise,” is assumed to be partially known (a nominal plant plus a bounded deviation). The considered approach consists of two consecutive steps. At the first step, the application of a sliding-mode-type algorithm is suggested, providing a finite-time equivalence of the original stochastic process with unknown parameters to an auxiliary one. Such an “equivalence” does not cancel the noise effects, but allows one to identify the model in the “regression form” for a sufficiently short time and, simultaneously, to transform the dependent noise, keeping bounded uncertainties as an external unmeasured dynamics. At the second step the least squares method with a scalar forgetting factor (LSMFF) is applied to estimate time-varying parameters of the given model. A convergence zone analysis is presented. A numerical example illustrates the effectiveness of the proposed approach.     

Experimental study on a novel polarization state generator

Duetothe spoilageinduced bythe polarization-relatedeffects (PRE) in high-speed(≥10 Gb/s/channel) opti-cal fiber communication systems ,it is necessary to in-vestigate the effect of PRE on optical components andentire transmission systems .In general , PR…     

On the communication complexity of zero-knowledge proofs

The fact that there are zero-knowledge proofs for all languages in NP (see [15], [6], and [5]) has, potentially, enormous implications to cryptography. For cryptographers, the issue is no longer “which languages in NP have zeroknowledge proofs” but rather “which languages in NP have practical zeroknowledge proofs.” Thus, the concrete complexity of zero-knowledge proofs for different languages must be established. In this paper we study the concrete complexity of the known general methods for constructing zero-knowledge proofs. We establish that circuit-based methods, which can be applied in either the GMR or the BCC model, have the potential of producing proofs which can be used in practice. Then we introduce several techniques which greatly reduce the concrete complexity of circuit-based proofs, and we show that these techniques lead to zero-knowledge proofs of knowledge. Finally, we show how to combine the techniques of Kilian, Micali, and Ostrovsky, for designing zero-knowledge proofs with only two envelopes, with some of our techniques for reducing the number of bits which the prover must commit to. Supported in part by NSA Grant No. MDA90488-H-2006. Supported in part by NSF Grant No. CCR-8909657.     

OS-CFAR and CMLD threshold optimization in distributed systems using evolutionary strategies

This paper proposes an improvement of the threshold optimization in distributed ordered statistics constant false alarm rate and censored mean level detector using Evolutionary Strategies (ESs). The target is assumed to be Rayleigh distributed and the observations are independent from sensor to sensor. Two fusion rules; “AND” and “OR” were considered. An ES was tested and a comparison with a genetic algorithm improved by a tournament selection was also analyzed. Among a variety of evolution strategies, the most popular proposed in the literature are the strategy (μ, λ) and the strategy (μ + λ). We proposed an (μ + λ) evolution strategy, by which a self-adaptation mutation is used. The results showed that, although the ES is more difficult to implement and is in a certain manner slower than the GA, it improves the performance of the system.     

Photo CVD system for silicon nitride film

An ultraviolet light excitation photo CVD system for silicon nitride film deposition, in which the use of mercury photo-sensitizer and the undesirable wall deposition onto the optical window inside are eliminated, has been developed. The elimination of the use of mercury sensitizer is achieved by employing direct photolysis of SiH₄/NH₃ gas mixture, using 185 nm light emitted from a low pressure mercury lamp. The wall deposition prevention is achieved by inserting an optically transparent “separator plate” with a number of through-holes on its plane area underneath the optical window and by draining inert gas into the reaction chamber through this “separator plate.” With this system, silicon nitride films have been deposited without marked degradation of deposition rate, keeping a reasonable deposition rate of about 40 A/minute. The inert gas used for wall deposition prevention has no influence on the properties of deposited films.     

ENTROPY IMMUNITY OF FEEDFORWARD NETWORKS

Siegenthaler's“Correlation Immunity”concept has been improved in this paper.From practical points of view,the new concept is more powerful than the original one in avoid-ing the trade-off between“the order of correlation immunity”and“the linear complexity”of keystreams in cipher system.Bent functions are also introduced into the studies of linear approxima-tion and entropy immunity for feedforward networks.New results and new methods are presentedalso.     

Some estimates pertaining to sensitivity and robust stability of input-output systems

The estimates derived in this paper strengthen the available results on sensitivity and robust stability of input-output systems. Two types of estimates are discussed: the “sensitivity type”, which establishes a bound for the output change when the system is perturbed but the input remains the same, and the “robustness type”, which gives a bound for the output change when the input changes but the perturbation does not. First, estimates for general systems over abstract extended spaces are derived; these results are then applied to (1) two frequently used control configurations, and (2) systems governed by vector integral and differential equations on the time domain [0, ∞). The applications of the estimates are illustrated by several examples. This research was supported by the National Science Foundation under Grant #DMS-9102910     

Interconnect Driver Design for Long Wires in Field-Programmable Gate Arrays

Each new semiconductor technology node brings smaller, faster transistors and smaller, slower wires. In particular, long interconnect wires in modern FPGAs now require rebuffering at interior points in the wire. This paper presents a framework for designing and evaluating long, buffered interconnect wires in FPGAs with near-optimal delay performance using HSPICE-derived delays. Given a target physical wire length, width, and spacing, the method determines the number, size, and position of buffers required to obtain the fastest signal velocity for programmable interconnect. While traditional hand-calculations used for ideal repeater placement can be used, they are not very accurate and ignore practical constraints such as the overhead effects of front-end multiplexing and driving logic, “finite” wire length, and a discrete number of repeaters. A metric introduced during the design is the “path delay profile”, or the arrival time of a signal at different points of a long wire. This method is used to design buffering strategies for interconnect based on 0.5, 2, and 3 mm wire lengths in 180 nm technology. These interconnect designs are coded into VPR along with an improved timing analyzer which accurately determines the “path delay profile” arrival times. Using VPR, average critical-path delay is reduced by 19% for 0.5 mm wires and by up to 46% for 3mm wires over previous designs.

Non-Equilibium Al-Ga interdiffusion in MOCVD reactor annealed AIGaAs quantum well heterostructures

AlGaAs-GaAs quantum well heterostructures have been annealed in an atmospheric pressure MOCVD reactor under an AsH₃/H₂ ambient. Photoluminescence spectra show a uniform and reproducible increase in the effective quantum well band-gap. Energy shift data indicate that Al-Ga interdiffusion occurs under “non-equilibrium” conditions resulting in depth-dependent Al-Ga interdiffusion such that quantum wells close to the surface disorder less than those further away. Activation energies vary from approximately 5.1–5.2 eV for the “equilibrium” case to 3.2–3.6 eV for the “non-equilibrium” case. These results suggest that caution must be exercised in using reported activation energies to characterize Al-Ga interdiffusion for photonic device fabrication. IBM Graduate Fellow Howard Hughes Doctoral Fellow     

First direct observation of EL2-like defect levels in annealed LT-GaAS

Nonstoichiometric arsenic-rich GaAs grown at low temperatures by molecular beam epitaxy (LT-GaAs) has been found to be semi-insulating after high-temperature annealing. The origin of this technologically important conversion is not yet fully understood. In order to study this effect, we performed photocurrent measurements on p-LT GaAs-n diodes in the spectral range between 0.75 and 1.5eV at 8K. The photocurrent spectra revealed the following features which are unique to the EL2 level: photoquenching, characteristic photoionization transitions to conduction band minima and a presence of a broad band due to the effect of auto-ionization from the excited state. Moreover, modeling of the optical excitation process using realistic band structure demonstrates that these features cannot be explained by “internal photoemission” originating from As precipitates, as the “buried Schottky barrier model” predicts. This is the first direct experimental evidence for the existence of EL2-like defect levels and their importance for understanding the optical and electronic properties of annealed LT-GaAs.     

Target software generation: an approach for automatic mapping of SystemC specifications onto real-time operating systems

In this paper we present a new approach for automated target code generation for given real-time operating systems out of SystemC to support platform independent software development. Since SystemC becomes the most important language in electronic system level design, the support of a seamless design flow becomes an important task. During the system design process, SystemC is used to develop a “Golden Reference Model” that provides a well-suited platform for specification, simulation, and verification of embedded systems. Based on the “Golden Reference Model,” an important task of the design process is to map applications, that have been described either in C++ or directly in SystemC, to the specific real-time operating system which is running at the target processor. Since a manual mapping approach is time-consuming and error-prone, the mapping process should be performed automatically. This paper presents a new method for automated generation of code for a specified operating system just by using an abstract XML representation of the RTOS API.     

Crystallographic evolution of microstructure in thin film processing: Part II. Grain boundary structure

The technique of electron backscattered diffraction is used to charactcrize the microtexture and mesotexture of grain neighborhoods in an annealed thin film of Al₉₇Ge₃ on thermally oxidized silicon. Of the microstructural features present in this material, a “sunken” (or “collapsed”) grain neighborhood is examined in terms of its mesotexture. The representation of crystallographic orientation between a “sunken” grain and its surrounding neighbors is assessed using inverse pole figures and Rodrigues-Frank (R-F) space orientation mapping. The two types of mappings are compared and detailed calculations of R-F space are shown. The advantages of the R-F space representation are illustrated. The total number of grains examined is 78 while the number of axis-angle pairs is 72. The microtexture is a strongly preferred < 111> parallel to the substrate normal while the mesotexture is comprised of low angle boundaries and fiber mesotexture as indicated by a R-F map.     

Template approaches to growth of oriented oxide heterostructures on SiO2/Si

A template approach to growing highly oriented ferroelectric oxide heterostructures on SiO₂/Si substrates is presented. In this method, a thin “template” of a layered perovskite is used to induce the growth of the subsequent layers in the desired orientation. The efficacy of this “template” approach is illustrated through the example of growth of ferroelectric La-Sr-Co-0/Pb-Zr-Ti-O/La-Sr-Co-O heterostructures on SiO₂Si. Discrete test capacitors fabricated from these heterostructures grown using the template approach exhibit remnant polarization values in the range of 10–15 μ C/cm² and show very little degradation after 10¹¹ bipolar fatigue cycles. In contrast, test capacitors fabricated without the template layer showed very little crystallographic texture and poor ferroelectric properties.