A multitarget sputtering machine with a water-cooled rotating substrate table has been modified to produce films on 75 mm × 75 mm wafers which map large portions of ternary phase diagrams. The system is unconventional because the stoichiometries of the elements sputtered on the wafer vary linearly with position and in an orthogonal manner. Subsequent screening of film properties is therefore quite intuitive, since the compositional variations are simple. Depositions are made under continuous rotation, so either intimate mixing of the elements (fast rotation) or artificial layered structures (slow rotation) can be produced. Rotating subtables mounted on the main rotating table hold the 75 mm × 75 mm substrates. Stationary mask openings over the targets and mechanical actuators that rotate the subtables in a precise manner accomplish the linear and orthogonal stoichiometry variations. Deposition of a film spanning the range SiSn x Al y (0 < x, y < 1), with Sn content increasing parallel to one edge on the wafer and Al content increasing in a perpendicular direction, is given to illustrate the effectiveness of the method. Since the system was easily and inexpensively built, it has enabled our research program in combinatorial materials synthesis to begin without large scale funding.

Si 1Ϫx Sn x samples for 0 Ͻ x Ͻ 0.5 were prepared by magnetron sputtering using a combinatorial materials science approach. The room-temperature resistivity and X-ray diffraction ͑XRD͒ patterns of the samples were used to select materials having both an amorphous structure and good conductivity for further study. The reaction of lithium with amorphous Si 0.66 Sn 0.34 was then studied by electrochemical methods and by in situ XRD. The electrode material apparently remains amorphous throughout all portions of the charge and discharge profile, in the range 0 Ͻ x Ͻ 4.4 in Li x Si 0.66 Sn 0.34. No crystalline phases are formed, unlike the situation when lithium reacts with tin. Using the Debye scattering formalism, we show that the XRD patterns of the a-Si 0.66 Sn 0.34 starting material and a-Li 4.4 Si 0.66 Sn 0.34 can be explained by the same local atomic arrangements as found in crystalline Si and Li 4.4 Si or Li 4.4 Sn, respectively. In fact, the in situ XRD patterns of a-Li x Si 0.66 Sn 0.34 , for any x, can be well approximated by a linear combination of the patterns for x ϭ 0 and x ϭ 4.4. This suggests that predominantly only two local environments for Si and Sn are found at any value of x in a-Li x Si 0.66 Sn 0.44. However, based on differential capacity vs. potential results for Li/a-Si 0.66 Sn 0.34 there is no evidence for two-phase regions during the charge and discharge profile. Thus, the two local environments must appear at random throughout the particles. We speculate that the charge-discharge hysteresis in the voltage-capacity profile of Li/ a-Li x Si 0.66 Sn 0.34 cells is caused by the energy dissipated during the changes in the local atomic environment around the host atoms.

Ballmilling of In and Sb has been used to produce InSb for use in electrochemical and in situ X-ray diffraction studies ͑XRD͒ of Li/1 M LiPF 6 ethylene carbonate:diethyl carbonate/InSb cells. The cell capacity decays rapidly when cycled between 0 and 1.3 V, while the capacity reduction is less pronounced when cycling is restricted to the 0.65-1.4 V range. In situ XRD studies reveal that Li 3 Sb and In are formed during the first plateau ͑above 0.65 V͒, according to the reaction 3Li ϩ InSb → Li 3 Sb ϩ In. The indium product subsequently reacts with Li forming the InLi x phases InLi and In 4 Li 7 in sequence. When cells are cycled above 0.6 V ͑i.e., in the absence of InLi x formation͒ capacity retention improves significantly, remaining relatively constant near 250 mAh/g. Detailed in situ XRD studies of these cells suggest that 0.27 Li atoms per InSb may be intercalated during a sharp drop in the cell potential, according to the reaction xLi ϩ InSb Li x InSb (x max ϭ 0.27). This intercalation accounts for only a small ͑about 30 mAh/g͒ fraction of the overall capacity of 680 mAh/g. Consequently, it appears that the reactivity of In and Sb with Li, not the structure type, determines the reaction path. Therefore, InSb is not an attractive intercalation host for Li, in contrast to the claims made in the literature.In the search for negative electrode ͑anode͒ materials for use in lithium-based batteries, it has been recently proposed 1 that intermetallic compounds with the zinc blende structure may be attractive candidates. The suggestion is derived in part from the availability of interstitial Li insertion sites as readily seen along a ͓110͔ projection of the zinc blende structure. At room temperature and atmospheric pressure InSb crystallizes in the cubic zinc blende structure (F4 3m no. 216͒, and so in a recent paper 1 the electrochemical and structural characteristics of this prototype compound were tested to determine its effectiveness as a Li insertion host. It was reported that two Li atoms could be incorporated into InSb to form a hitherto unknown Li 2 InSb phase that displays very little ͑5.6%͒, volume expansion ͑relative to InSb͒. The new phase was claimed to form according to the reaction 2Li ϩ InSb → Li 2 InSb, while a subsequent reaction xLi ϩ Li 2 InSb → Li 2ϩx In 1Ϫx Sb ϩ xIn (x max ϭ 1) forms Li 3 Sb and In. The electrochemical cell exhibited good capacity retention ͑300 mAh/g͒ over 22 cycles. This prompted the authors to suggest that the results open up exciting possibilities for identifying other zinc blende insertion electrodes.Earlier work ͑not referenced by the authors of Ref. 1͒ on the reaction of lithium with InSb showed that only a small amount of Li could be intercalated within the InSb structure from solutions of n-butyllithium in hexane. Herren and Walsoe de Reca 2 found x ϭ 0.053 in Li x InSb was the limiting composition under these conditions.As suggested by the authors of Ref. 1, further work is required to determine the exact structural transformations that occur during the discharge and c...

Collagen fibrils are the main constituent of the extracellular matrix surrounding eukaryotic cells. Although the assembly and structure of collagen fibrils is well characterized, very little appears to be known about one of the key determinants of their biological function-namely, the physico-chemical properties of their surface. One way to obtain surface-sensitive structural and chemical data is to take advantage of the near-field nature of surface- and tip-enhanced Raman spectroscopy. Using Ag and Au nanoparticles bound to Collagen type-I fibrils, as well as tips coated with a thin layer of Ag, we obtained Raman spectra characteristic to the first layer of collagen molecules at the surface of the fibrils. The most frequent Raman peaks were attributed to aromatic residues such as phenylalanine and tyrosine. In several instances, we also observed Amide I bands with a full width at half-maximum of 10-30 cm(-1). The assignment of these Amide I band positions suggests the presence of 3(10)-helices as well as α- and β-sheets at the fibril's surface.

The electrochemical performance of Si electrodes using polyvinylidene fluoride (PVDF) binder heated at different temperatures ranging from 150°C to 350°C was investigated. Compared to unheated electrodes that have no capacity after the first formation cycle, the heat treated electrodes show an increasingly improved cycling performance as the heating temperature increases from 150°C to 300°C. In particular, Si electrodes heated at 300°C retain a specific capacity of about 600 mAh/g for 50 cycles with a lower cutoff potential of 0.170 V vs Li/Li + . The reasons for such improvements are considered based on results from thermal analysis, optical microscopy and adhesion tests. It is suggested that heat treatment improves the binder distribution, the adhesion to the Si particles and to the substrate, thereby leading to a better cycling performance.2