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HfO2 layers, 25-Å thick, were grown by cyclic Hf sputter deposition and room temperature oxidation steps on chemically oxidized Si(001). Subsequent in situ annealing and TiN deposition yield a high- \kappa gate-stack for which the original 8-Å-thick SiO2 layer is eliminated, as confirmed by transmission electron microscopy. Transistors fabricated with this gate-stack achieve an equivalent oxide thickness in inversion T_{\rm inv} =9.7 Å, with a gate leakage J_{g} =0.8 A/cm2. Devices fabricated without in situ annealing of the HfO2 layer yield a Tinv which increases from 10.8 to 11.2 Å as the oxidation time during each HfO2 growth cycle increases from 10 to 120 s, also causing a decrease in Jg from 0.95 to 0.60 A/cm2, and an increase in the transistor threshold voltage from 272 to 294 mV. The annealing step reduces Tinv by 1.5 Å (10%) but also increases the gate leakage by 0.1 A/cm2 (30%), and causes a 61 mV reduction in Vt . These effects are primarily attributed to the oxygen-deficiency of the as-deposited HfO2, which facilitates both the reduction of an interfacial SiO2 layer and a partial phase transition to a high- $\kappa $ cubic or tetragonal HfO2 phase. [ABSTRACT FROM AUTHOR]

We investigate the determining mechanisms of the inversion-layer capacitance Cinv in the high-k/metal gate stacks, focusing on the two perturbative effects related with the dielectric properties. Those effects are the penetration of inversion-layer carriers into the dielectrics with a finite potential barrier and the image potential acting on the carriers adjacent to the dielectrics with permittivity different from that of the silicon substrate. The experimental and the theoretical analyses of the Cinv dependency on the crystal orientation of silicon substrates enable us to separate the two effects and to prove that the observed Cinv modulation in the high- k/metal gate stacks is attributable not to the image potential effect, but to the penetration effect. Moreover, we investigate the reduction of the total gate capacitance due to the Cinv in the advanced gate stacks scaled down to 0.66-nm equivalent oxide thickness. The influence of the elementary composition, the physical thickness, and the interface layer on a scaling loss due to the Cinv is experimentally evaluated. [ABSTRACT FROM AUTHOR]

The inversion-layer capacitance Cinv of electrons in high-k/metal gate stacks (HKMGs) is studied theoretically and experimentally from the viewpoint of the penetration of electrons into the dielectrics. The numerical calculation of Cinv in the dielectric/substrate bilayer structure has clarified the influence of penetration on Cinv. Cinv in an HKMG is evaluated experimentally and is compared with the computational predictions in terms of the dependence on the dielectric boundary and the silicon crystal orientation. The consistency of the experiment and the calculation is the first evidence for the considerable modulation of Cinv due to penetration in the actual HKMG. Moreover, the dependence of Cinv on substrate biasing is investigated. The detailed analysis of Cinv in the system where the confinement of the inversion layer is intentionally changed has led to a further understanding of Cinv determined by penetration. [ABSTRACT FROM PUBLISHER]

Ensuring anonymity in wireless and hoc networks is a major security goal. Using traffic analysis, the attacker can compromise the network functionality by correlating data flow patterns to event locations/active areas. In this paper we present a novel Scalable Anonymous Protocol that hides the location of nodes and obscure the correlation between event zones and data flow from snooping adversaries. We quantify the anonymity strength of our protocol by introducing a new anonymity metric: Degree of Exposure Index. Our protocol is designed to offer flexible tradeoffs between degree of anonymity and communication-delay overhead. [ABSTRACT FROM AUTHOR]

Wireless Mobile Ad Hoc Networks are particularly vulnerable due to their fundamental characteristics such as an open medium, dynamic topology, distributed cooperation, and constrained capability. Location information of nodes can be critical in wireless ad hoc networks, especially in those deployed for military purposes. In this paper, we present two Protocols for anonymous routing to prevent location disclosure attacks. The Protocol for Anonymous Routing (PAR) guarantees absolute anonymity, which itself might cause problems as it would become hard to identify malicious and misbehaving nodes. PAR-Enhanced trades off some anonymity to enable detection of malicious and misbehaving nodes. [ABSTRACT FROM AUTHOR]

We propose to use IEEE 802.22 networks as a natural interconnection between energy-constrained networks, such as sensor networks, and the Internet. In this interconnection scenario, we propose Activecast, broadcast designed as a continuation of the IEEE 802.22 broadcast on sensor networks. Activecast effectively transmits a query to all active sensors in the network. Activecast minimizes the number of retransmitted messages while maintaining high reachability. Activecast requires minimum communication overhead, yet performs very well in the presence of various environmental constrains. Activecast can also be integrated to any sleep based sensor protocol, as it does not make any assumptions on the underlying wake up scheduling protocol and wake up times/durations of the sensors. We study the properties of Activecast by analysis and simulations while also considering irregular radio coverage of sensors. [ABSTRACT FROM AUTHOR]

In this paper we present Clustering Protocol for Sensor networks (CPS). Clustering techniques are used by different protocols and applications to increase scalability and reduce delays in sensor networks. Examples include routing protocols, and applications requiring efficient data aggregation. Our approach is based on the Covering Problem that aims at covering an area with minimum number of circular disks. CPS is a lightweight protocol that does not require any neighborhood information and imposes low communication overhead. We present simulation results to show the efficiency of CPS in both ideal cases and randomly distributed networks. Moreover, CPS is scalable with respect to density and network size. [ABSTRACT FROM AUTHOR]

We present Delay-Energy Aware Routing (DEAP) a novel protocol for heterogeneous wireless ad hoc networks. DEAP is a crosslayer scheme that: first, manages adaptively the energy control by controlling the wakeup cycle of sensors based on the experienced packet delay; and second, rout packet in each hoc by distributing the load a group of neighboring nodes. The primary result of DEAP is that it enables a flexible and wide range of tradeoffs between the packet delay and the energy consumption. Therefore, DEAP supports delay sensitive applications of heterogeneous networks that include sensors and actors. DEAP is scalable to the change in network size, node type, node density and topology. DEAP accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed, while DEAP does not count on actors, it takes advantage of them, and uses their resources when possible, thus reducing the energy consumption of sensor nodes. Through analysis and simulation evaluations, we show that DEAP improves the packet delay and network lifetime compared to other protocols. [ABSTRACT FROM AUTHOR]

Abstract: Sodium dodecyl sulfate (SDS) self assembles at hydrophobic graphite surfaces forming linear parallel hemicylinders with approximately 5nm spacing between adjacent hemicylinders. In this paper, we report the effect of cosurfactants on the SDS surface micelle structures. It is known from the literature that cosurfactants influence the relaxation times of bulk phase micelles. Specifically, the relaxation times of SDS micelles increase dramatically when cosurfactants, such as non-ionic 1-dodecanol (C12OH) or cationic dodecyl trimethyl ammonium bromide (C12TAB) are added, resulting in the formation of stable micelles. Soft contact AFM imaging was used to determine if these increased relaxation times in bulk solution influence the formation of surface micelle structures at the graphite surface. Surface micelles formed by adsorption from SDS only solutions were significantly different from those surface micelles formed from mixed surfactant solutions. The addition of cosurfactants produced kinks and disrupted the otherwise highly ordered linear hemicylindrical SDS structures observed at graphite surfaces. In one case (SDS/C12OH) swollen surface micelles with a spacing of more than 8nm were observed. Finally, whereas surface micelles form instantaneously from SDS only solutions, the time taken for the equilibrium surface state to be established in the presence of the C12OH cosurfactant was found to be more than 4h. [Copyright &y& Elsevier]

We present Geometric Broadcast for Heterogeneous Sensor Networks (GBS), a novel broadcasting protocol for heterogeneous wireless sensor and actor networks. While broadcasting is a very energy expensive protocol, it is also widely used as a building block for a variety of other network layer protocols. Therefore, reducing the energy consumption by optimizing broadcasting is a major improvement in heterogenous sensor networking. GBS is a distributed algorithm where nodes make local decisions on whether to transmit based on a geometric approach. GBS does not need any neighborhood information and imposes very low communication overhead. GBS is scalable to the change in network size, node type, node density and topology. Furthermore it accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed, GBS takes advantage of actor nodes, and uses their resources when possible, thus reducing the energy consumption by sensor nodes. Through simulation evaluations, we show that GBS is very scalable and its performance is improved by the presence of actors. At the best of our knowledge, GBS is the first broadcast protocol designed specifically for heterogeneous sensor and actor networks. [ABSTRACT FROM AUTHOR]

Sensor networks usually operate under very severe energy restrictions. Therefore, sensor communications should consume the minimum possible amount of energy. While broadcasting is a very energy-expensive protocol, it is also widely used as a building block for a variety of other network layer protocols. Therefore, reducing the energy consumption by optimizing broadcasting is a major improvement in sensor networking. In this paper, we propose an optimized Broadcast Protocol for Sensor networks (BPS). The major novelty of BPS is its adaptive-geometric approach that enables considerable reduction of retransmissions by maximizing each hop length. BPS adapts itself and gets the best out of existing radio conditions. In BPS, nodes do not need any neighborhood information, which leads to low communication and memory overhead. We analyze the worst-case scenario for BPS and show that the number of transmissions in such a scenario is a constant multiple of those required in the ideal case. Our simulation results show that BPS is very scalable with respect to network density. BPS is also resilient to transmission errors. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel lightweight protocol for data integrity in wireless sensor networks. Our protocol is based on a leapfrog strategy in which each cluster head verifies if its previous node has preserved the integrity of the packet using the secret key it shares with two hop uptree nodes. The proposed protocol is simple. The analysis and simulation results show that the protocol needs very few header bits, as low as three bits, thus resulting in negligible bandwidth overhead; the protocol poses very low computational overhead, it needs to compute just a hash as compared to multiple complex operations required by any cryptographic implementation for verifying authenticity. [ABSTRACT FROM AUTHOR]

The design of the IF protocol makes it difficult to reliably identify the originator of an IF packet, causing the defense against Distributed Denial of Service attacks to become one of the hardest problems on the Internet today. Previous solutions for this problem try to traceback to the exact origin of the attack by requiring every router's participation. For many reasons this requirement is impractical and the victim results with an approximate location of the attacker. Reconstruction of the whole path is also very difficult due to the sheer size of the Internet. This paper presents lightweight schemes for tracing back to the attack-originating AS instead to the exact origin itself. Once the attack-originating AS is determined, all further routers in the path to the attacker are within that AS and under the control of a single entity; which can presumably monitor local traffic in a more direct way than a generalized, Internet scale, packet marking scheme can. We furthermore, provide a scheme to prevent compromised routers from forging markings. [ABSTRACT FROM AUTHOR]

In this letter, we investigated a dominant mechanism for leakage reduction by the incorporation of La in a \HfO2\/SiO2 gate stack. We compared the experimental data for the leakage current for the La-doped \HfO2 \/SiO2 gate stack and the calculation for tunnel current through the gate stack, assuming that the La-induced dipole increases the barrier height of \HfO2 for electrons from the substrate. The agreement between the experimental data and calculated values strongly suggests that the main cause for leakage reduction is the effective barrier height modulation induced by the interface dipole. [ABSTRACT FROM AUTHOR]

Strained-silicon-on-insulator (SSOI) undoped-body high-\kappa/metal-gate n-channel fin-shaped field-effect transistors (nFinFETs) at scaled gate lengths and pitches (i.e., LGATE\sim\!\!\25\ nm and a contacted gate pitch of 130 nm) were fabricated using a gate-first flow. A “long and narrow” fin layout (i.e., fin length \sim\!\!\1\ \mu\m) was leveraged to preserve uniaxial tensile strain in the transistors. These devices exhibit drive currents suitable for high-performance logic technology. The change in the slope of RON - LGATE\ (\rm dRON/\dLGATE), transconductance GMSAT, and injection velocity (vinj) measurements indicate a \sim15% mobility-induced ION enhancement with SSOI relative to SOI nFinFETs at ultrashort gate lengths. Raman measurements conducted on SSOI substrates after fin formation demonstrate the preservation of \sim1.3-GPa uniaxial tensile strain even after 1100 ^\circ\C annealing. [ABSTRACT FROM AUTHOR]

Sulfur passivation of Ge(100) is achieved using aqueous ammonium sulfide (NH4)2S(aq). The passivation layer is largely preserved after atomic layer deposition of the high-κ dielectric material HfO2 when sufficiently low growth temperatures (e.g., 220 °C) are employed. Oxygen incorporation is moderate and results in an electrically passivating GeOS interface layer. The HfO2/GeOS/Ge gate stack exhibits lower fixed charge and interface state density than a more conventional HfO2/GeON/Ge gate stack fabricated via an ammonia gas treatment. [ABSTRACT FROM AUTHOR]

We have investigated the electron mobility limited by the remote charge scattering, µRCS, in the thin silicon body (≤8 nm) double-gated metal–oxide–semiconductor field-effect transistors (MOSFETs), focusing on its dependency on the body thickness and the silicon surface orientation. In order to predict the µRCS in such an unprecedented MOSFET system, the adequacy of physical models used in the computation was verified by comparing the computational results with the experimentally determined µRCS from the actual bulk MOSFETs with high-k dielectric fabricated on the (100) and (110) silicon substrates. It has been discovered for the first time that the µRCS is dropped to less than half of the bulk device's µRCS when the body thickness is 5 nm and that the µRCS lowering derived from the body thickness reduction is more serious in the (110)-oriented surface than in the (100)-oriented surface. These mobility trends have been quantitatively explained by the effective mass difference between the two surfaces as well as by the carrier confinement in the metallurgically defined narrow silicon body. These observations indicate the great importance of the systematic reduction of charged traps in high-k gate dielectrics in the advanced devices. [ABSTRACT FROM AUTHOR]

A detailed comparison of high-k/metal gate stacks fabricated on the (100)- and (110)-oriented substrates has been made. We have verified that there is no structural difference between the gate stacks on the two substrates. The orientation independence of our gate stacks with the high-quality high-k/silicon interface for both substrates reveals the intrinsic effects of the crystal orientation on the high-k/metal gate devices. This is the first direct evidence that the inversion carrier quantization dependency on the crystal orientations dominates the total gate capacitance in the high-k/metal gate system. The analysis of the electron and hole mobilities highlights the fact that the scattering mechanisms inherent in the high-k/meta gate stacks limit the mobility enhancement and reduction driven by the effective mass change. No significant difference in the threshold voltage instability under the positive or negative gate bias stress is observed for the two substrates. Therefore, the optimized high-k/metal gate stacks enable us to gain certain benefits from the limited modulation of the mobility without sacrificing the stability of the threshold voltage. [ABSTRACT FROM AUTHOR]

We extensively investigated the physical origin of the threshold voltage VTH modulation by the Ge channel ion implantation (I/I) in HfO2/TiN/polycrystalline Si gate stack systems. The possible VTH modulation factors were carefully distinguished from each other by changing the channel dopant concentration and the thickness of the gate dielectric films. It was found that the changes in energy-band offset and dopant concentration in the channel region are minor factors of the VTH modulation. However, it was also found that ΔVTH is sensitive to the oxidation condition of the interfacial oxide layer; a longer oxidation induces a larger ΔVTH. From the X-ray spectroscopy, we found that a Ge pile-up at the interfacial layer/channel interface occurs, and that the VTH modulation range correlates well with the amount of piled-up Ge. [ABSTRACT FROM AUTHOR]

The influence of the crystal orientation difference between (100) and (110) silicon substrates on characteristics of La2O3- and Al2O3-capped HfO2 dielectric metal–oxide–semiconductor field-effect transistors has been investigated. We observed that the equivalent oxide thickness of the capped devices varies according to the crystal orientation, indicating that the two substrates are not equal in the gate stack scalability within a sub-nanometer regime. We found that the mobility dependency on the crystal orientation is reduced by additional scattering associated with the capping films, suggesting the difficulty to derive maximum benefit from an inherent difference in the mobility depending on the crystal orientation. [ABSTRACT FROM AUTHOR]