Crossbar device

Single-walled carbon nanotubes (SWNTs) had been considered for the crossbar components of the defect-tolerant molecular computers but they have been found to be too difficult to handle due to their insolubility and their tendency to form bundles or ropes. Instead, metallic nanowires have become the materials of choice used in the construction of the crossbar devices, with ultrahigh-density lattices and circuits being built, having groups of nanowires 8 nm in diameter and 16 nm apart in layers perpendicular to each other to create nanowire junction densities of 1011 per cm2.52 The process does not depend on self-assembly but rather on molecular beam epitaxy. 

In the most recent iteration of the feedback loop which relates molecular structure to solid-state device performance, the fast bistable [2]rotaxane 11" has been superseded " by the modified and improved version shown in Fig. 1.15, namely, the [2]rotaxane The impetus for this iteration was at least two-fold (1) to produce a molecular switch in which the bistable rotaxane starts off exclusively in one, and only one, of its two possible co-conformations and (2) to incorporate into this all-or-nothing switch enhanced oxidative stability by removing all of the phenolic residues from the hydrophilic stopper. The rotaxane, which was obtained (Fig. 1.15) by the now well-established templation protocol, has been incorporated by the familiar fabrication procedures into an 8 x 8 crossbar device (Fig. 1.16(a)). Fig. 1.16(b) demonstrates one of these 64-bit devices in operation with the exception of one of the wires, i.e., 56 out of the 64 bits can be switched. This device has been used to store (Fig. 1.16(c)) the letters DARPA in ASCII code the lifetime of the switch-closed state of this devices is about 10 minutes. The proposed electromechanical switching mechanism for the bistable [2]rotaxane which is outlined in Fig. 1.17, merits comparison with that already discussed in Fig. 1.16 for the bistable [2]rotaxane In the case of it is proposed that oxidation of the TTF unit to its radical cation (TTF ) occurs when a +2 V bias is applied across the bistable [2]rotaxane and the tetracationic cyclophane moves to encircle the... 

Deng J, Hofbauer W, Chandrasekhar N, Shea SJ (2007) Metallization for crossbar molecular devices. Nanotechnology 18(15) 155202... 

There are two DSP-32s per processor module . The master (with external memory) is connected to the serial lines going to and from the crossbar switch. The slave is connected to external I/O devices such as A/D and D/A converters. It is... 

Besides self-assembly on the surface of metals, another example of self-assembly is the formation of Langmuir-Blodgett monolayers on the surface or at the interface of liquids.47,48 One approach to molecular-based electronic devices that has made use of self-assembled Langmuir-Blodgett films is the crossbar-based defect-tolerant approach to molecular computing 49 Rotaxane molecules that depend on physical dislocations within the molecule to produce switching functionality have been designed such that they will... 

It is probable that rather than using self-assembly to add any active molecules to the device architecture, the nanowires used to construct the devices will be precoated with active molecules via spin coating as shown by Lieber in his recent work.53 Specially doped silicon nanowires have also shown interesting properties in crossbar-based devices.54... 

More interesting observations were made on incorporation of the bistable catenane 134+ (Fig. 17.12) into a solid-state device.115 A monolayer of the catenane was transferred onto a photolithographically patterned polycrystalline silicon electrode. The patterning was such that the Langmuir film was deposited along several parallel lines of poly-Si on the electrode. A second set of orthogonally oriented wires was then deposited on top of the first set such that a crossbar architecture is obtained. This second set of electrodes consisted of a 5 nm thick layer of Ti, followed... 

The careful design and delicate synthesis of a number of catenanes and rotaxanes have led to their incorporation into monolayers, and then from these monolayers in the form of Langmuir-Blodgett films onto patterned silicon substrates. This step, followed by the deposition of a second metal layer in the perpendicular direction to form a crossbar, has resulted in the production of an ever-growing number of electrical devices in which the switching is carried out at junctions one molecule thick. 

There are many reports in the literature about interfaces and devices for preparation of blood samples on chip. Eor example, Jandik et al. used a laminar fluid diffusion interface to replace centrifugation and consequently reduced the preparation time from between 30-60 minutes to only five minutes . The H-filter has also been used to clean up biological samples. A sample, e.g. blood, is put into a reservoir at one end of one post of the H, and a diluent such as water or saline is placed in the reservoir at the other end. The two parallel laminar streams will flow along the crossbar of the H as a resnlt of hydrostatic pressnre. Smaller, more mobile analyte molecnles will cross the interface between streams qnickly, whilst heavier particles remain in the carrier stream. Conseqnently, by controlling the fluid velocity and the length of the channel, the process can be optimised. There are also devices for separating plasma from blood on a chip . ... 

Nodes often provide multiple sockets, each of which can accommodate a multicore chip (two or four sockets are common, and three-socket configurations exist as well). Figure 2.15 shows an example of a node architecture based on the quad-core AMD Opteron chip. Each chip has four cores (or processors, as we use the term here). Each core has its own first (LI) and second (L2) level caches. All four cores share the third level cache (L3). A crossbar switch connects the processors to two memory controllers for accessing off-chip memory. The crossbar has three additional high-speed links that can be used to connect other multicore chips or input/output devices. 

The main parts of the automated knife cutting system are a cutting device and a carriage in which the cutting device is fixed, a crossbar (beam), which carries the carriage... 

Figure , (a) Daily release of nafarelin from a cross-linked poly(ortho ester) (POE). Crossbar denotes minimum daily requirement of 0.4 //g/day for estms suppression. Conditions 7.4mm x 20 mm rods prepared from a 3-methyl-l,5-pentanediol prepolymer cross-linked with 1,2,6-hexanetriol and placed into pH 7.4 buffer at 37°C. (b) Percent of female rats showing estms suppression as a function of treatment time with nafarelin-containing POE rods. Devices were prepared from a 3-methyl-1,5-pentanediol prepolymer cross-linked with 1,2,6-hexanetriol and contained 3 wt.% LHRH analog. (After Heller et al, 1987.)... 

FIGURE 1 A series of 100-element crossbar circuits, the prominent circuits of molecular electronics. The molecule of interest is typically sandwiched between the intersection of two crossed wires. This very simple circuit can be used even in the presence of manufacturing defects and can be fabricated at dimensions that far exceed the best lithographic methods. The device densities in these circuits approach lO /cm for the smallest crossbars. 

DNA self-assembly could be used in a variety of ways to solve this problem molecular components (e.g., AND, OR, and NOT gates, crossbars, routing elements) could be chemically attached to DNA tiles at specific chemical moieties, and subsequent self-assembly would proceed to place the tiles (and hence circuit elements) into the appropriate locations. Alternatively, DNA tiles with attachment moieties could self-assemble into the desired pattern, and subsequent chemical processing would create functional devices at the positions specified by the DNA tiles. None of these approaches has yet been convincingly demonstrated, but it is plausible that any of them could eventually succeed to produce two- or three-dimensional circuits with nanometer resolution and precise control of chemical structure. 

All the dynamic measurements thus far mentioned furnish the complex Young s modulus in the fiber direction. The shear modulus at right angles can be measured by torsional vibrations of the fiber itself, using a light crossbar or disc to provide the amount of inertia for a compound oscillating system in forced or free vibration. An example is shown in Rg. 7-7, where the forced vibrations are driven by an electrostatic device. Here the analog of equation 13 of Chapter 6 is ... 

Additionally, if SWNTs are to be used as the crossbars, connection of molecular switches via covalent bonds introduces sp -hybridized carbon atom linkages at each junction, disturbing the electronic nature of the SWNT and possibly rendering useless the SWNTs in the first place. Non-covalent bonding of the device molecule to the SWNT will probably not provide the conductance necessary for the circuit to operate. Therefore, continued work is being done to devise and construct crossbar architectures that address these challenges. 

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