Plasma-enhanced atomic layer deposition of vanadium phosphate as a lithium-ion battery electrode material

Vanadium phosphate films were deposited by a new process consisting of sequential exposures to trimethyl phosphate (TMP) plasma, O2 plasma, and either vanadium oxytriisopropoxide [VTIP, OV(O-i-Pr)3] or tetrakisethylmethylamido vanadium [TEMAV, V(NEtMe)4] as the vanadium precursor. At a substrate temperature of 300 °C, the decomposition behavior of these precursors could not be neglected; while VTIP decomposed and thus yielded a plasma-enhanced chemical vapor deposition process, the author found that the decomposition of the TEMAV precursor was inhibited by the preceding TMP plasma/O2 plasma exposures. The TEMAV process showed linear growth, saturating behavior, and yielded uniform and smooth films; as such, it was regarded as a plasma-enhanced atomic layer deposition process. The resulting films had an elastic recoil detection-measured stoichiometry of V1.1PO4.3 with 3% hydrogen and no detectable carbon contamination. They could be electrochemically lithiated and showed desirable properties as lithium-ion battery electrodes in the potential region between 1.4 and 3.6 V versus Li+/Li, including low capacity fading and an excellent rate capability. In a wider potential region, they showed a emarkably high capacity (equivalent to three lithium ions per vanadium atom), at the expense of reduced cyclability.status: publishe

Atomic layer deposition of aluminum phosphate based on the plasma polymerization of trimethyl phosphate

Aluminum phosphate thin films were deposited by plasma-assisted atomic layer deposition (ALD) using a sequence of trimethyl phosphate (TMP, Me3PO4) plasma, O-2 plasma, and trimethylaluminum (TMA, Me3Al) exposures. In situ characterization was performed, including spectroscopic ellipsometry, optical emission spectroscopy, mass spectrometry and FTIR. In the investigated temperature region between 50 and 320 degrees C, nucleation delays were absent and linear growth was observed, with the growth per cycle (GPC) being strongly dependent on temperature. The plasma polymerization of TMP was found to play an important role in this process, resulting in CVD-like behavior at low temperatures and ALD-like behavior at high temperatures. Films grown at 320 degrees C had a GPC value of 0.37 nm/cycle and consisted of amorphous aluminum pyrophosphate (Al4P6O21). They could be crystallized to triclinic AlPO4 (tridymite) by annealing to 900 degrees C, as evidenced by high-temperature XRD measurements. The use of a TMP plasma might open up the possibility of depositing many other metal phosphates by combining it with appropriate organometallic precursors

Energy-efficient traffic engineering

The energy consumption in telecommunication networks is expected to grow considerably, especially in core networks. In this chapter, optimization of energy consumption is approached from two directions. In a first study, multilayer traffic engineering (MLTE) is used to assign energy-efficient paths and logical topology to IP traffic. The relation with traditional capacity optimization is explained, and the MLTE strategy is applied for daily traffic variations. A second study considers the core network below the IP layer, giving a detailed power consumption model. Optical bypass is evaluated as a technique to achieve considerable power savings over per-hop opticalelectronicoptical regeneration. Document type: Part of book or chapter of boo

Towards a deployment tool for wireless access networks with minimal power consumption

The power consumption of wireless access networks will become an important issue in the coming years. In this paper, the power consumption of base stations for mobile WiMAX, HSPA, and LTE is modelled. This power consumption is related to the coverage of the base station. The considered technologies are compared according to their energy efficiency for different bit rates at a bandwidth of 5 MHz. For this particular case and based on the assumptions of parameters of the specifications, HSPA is the least energy-efficient technology. Until a bit rate of 11 Mbps LTE is the most energy-efficient while for higher bit rates mobile WiMAX performs the best. Furthermore the influence of MIMO is investigated. A decrease of about 80% for mobile WiMAX and about 74% for HSPA and LTE for the power consumption per covered area is found for a 4*4 MIMO system compared to a SISO system. The introduction of MIMO has thus a positive influence on the energy efficiency of the considered technologies. The power consumption and coverage model for base stations is then used to develop a prediction tool for power consumption in wireless access networks