Scanning tunneling microscopy and spectroscopy investigations of QCA molecules

Manimaran, M.; Snider, Gregory L.; Lent, Craig S.; Sarveswaran, V.; Lieberman, Marya; Li, Zhaohui; Fehlner, Thomas P.

doi:10.1016/s0304-3991(03)00085-8

Cited by 25 publications

(13 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…as dots, so that electron transfer from dot to dot has minimal effect on the overall molecular structure [33][34][35][36][37][38][39][40][41][42][43]. Twodot half-cells [40][41][42] and four-dot cells [43] have recently been synthesized.…”

Section: Quantum-dot Cellular Automatamentioning

confidence: 99%

“…A local electric field provides a clocking signal which controls the activity of the cell and can smoothly switch it from an informationbearing 'active' state to a non-information-bearing 'null' state. Prototype QCA circuits have been fabricated using metal tunnel junctions in the single-electron regime [24][25][26][27][28][29][30][31][32] and considerable progress has been made towards implementing molecular QCA [33][34][35][36][37][38][39][40][41][42][43]. The QCA clocking scheme that has been developed relies on switching the cell to an active state adiabatically, that is, gently enough that it is always very close to its instantaneous ground state, applying the ideas of Landauer [34,38].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling

2006

View full text Add to dashboard Cite

We examine power dissipation in different clocking schemes for molecular quantum-dot cellular automata (QCA) circuits. 'Landauer clocking' involves the adiabatic transition of a molecular cell from the null state to an active state carrying data. Cell layout creates devices which allow data in cells to interact and thereby perform useful computation. We perform direct solutions of the equation of motion for the system in contact with the thermal environment and see that Landauer's Principle applies: one must dissipate an energy of at least k(B)T per bit only when the information is erased. The ideas of Bennett can be applied to keep copies of the bit information by echoing inputs to outputs, thus embedding any logically irreversible circuit in a logically reversible circuit, at the cost of added circuit complexity. A promising alternative which we term 'Bennett clocking' requires only altering the timing of the clocking signals so that bit information is simply held in place by the clock until a computational block is complete, then erased in the reverse order of computation. This approach results in ultralow power dissipation without additional circuit complexity. These results offer a concrete example in which to consider recent claims regarding the fundamental limits of binary logic scaling.

show abstract

Section: Quantum-dot Cellular Automatamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling

2006

View full text Add to dashboard Cite

show abstract

“…[1][2][3][4][5][6][7][8][9][10][11][12] One proposed architecture for such devices is based upon quantum dot cellular automata (QCA), in which binary information is encoded in the charge configuration of a single cell and transferred by electric coupling between neighboring QCA cells. [13][14][15][16][17] Implementation of QCA at the molecular level requires mixed-valence molecules with two or more oxidation-reduction centers, and such molecules have been shown to have the desired electronic properties using ensemble measurement techniques. 18,19 For the fabrication of devices, it is imperative to understand the changes in charge configuration that result when an electron tunnels between redox sites in a single molecule on a surface.…”

mentioning

confidence: 99%

Scanning Tunneling Microscopy of Mixed Valence Dinuclear Organometallic Cations and Counterions on Au(111)

Guo

Kandel

2009

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

Single-molecule electronic components are potential building blocks for next-generation electronic devices. One architecture for such devices is quantum dot cellular automata (QCA), in which binary information is encoded in the charge configuration of a single cell and transferred by electric coupling between neighboring cells. A single mixed-valence molecule with two oxidationreduction centers can serve as a QCA cell, and ensemble measurements have shown that such molecules may have the desired electronic properties. Scanning tunneling microscopy (STM) is used to image dinuclear metal complexes, trans-[Cl-(dppe) 2 Ru(CtC) 6 Ru(dppe) 2 Cl] (Ru2) on Au(111) at 77 K. Oxidation to Ru2 þ [PF 6 ] -creates an unbalanced charge that localizes on one end group of the otherwise symmetric Ru2 molecule. This electronic asymmetry appears in STM images, which also resolve the associated [PF 6 ] -counterions. Comparison of Ru2 and Ru2 þ monolayers show that Coulomb interactions create long-range ordering of Ru2 þ electronic charge. This is a requirement for functionality in a QCA device.SECTION Surfaces, Interfaces, Catalysis S ingle-molecule electronic components have been investigated as the building blocks for next-generation electronic devices. 1-12 One proposed architecture for such devices is based upon quantum dot cellular automata (QCA), in which binary information is encoded in the charge configuration of a single cell and transferred by electric coupling between neighboring QCA cells. 13-17 Implementation of QCA at the molecular level requires mixed-valence molecules with two or more oxidation-reduction centers, and such molecules have been shown to have the desired electronic properties using ensemble measurement techniques. 18,19 For the fabrication of devices, it is imperative to understand the changes in charge configuration that result when an electron tunnels between redox sites in a single molecule on a surface. 20 In our work, we present the scanning tunneling microscopy (STM) studies of dinuclear metal complexes, trans-[Cl(dppe) 2 Ru(CtC) 6 Ru(dppe) 2 Cl] (abbreviated as Ru2, dppe = diphenylphosphinoethane) on Au(111) at cryogenic temperature. Close-packed Ru2 molecules form monolayers with ordered stripes on Au(111) at 77 K. Ru2 þ [PF 6 ] -, the oxidation product of Ru2, has an extra charge which can tunnel between two metal-centered end groups. Ru2 þ cations are imaged also as a pair of dots on Au(111) and form similar striped monolayers, except that the two dots appear to have different contrast in STM images due to the extra charge localized in one end group. [PF 6 ] -anions are observed as a small dot resting next to the positively charged ends of Ru2 þ cations.The dinuclear metal complex Ru2 is composed of two Ru-centered phenylphosphine groups connected by a linear hexa-alkyne-bond linker, as shown in Figure 1A. While Ru2 is a neutral dinuclear complex with both Ru metal atoms in the þ2 valence state, oxidation to Ru2 þ results in a mixed-valence þ2/þ3 molecule with an odd electron that can tunnel be...

show abstract

“…However, for improvement in operation temperature and size of the QCA devices, the idea of molecular quantum-dot cellular automata (molecular QCA) devices (5), in which a QDC constructed from small metallic dots is replaced by a single molecule, was proposed. Toward the experimental operation of molecular QCA devices, syntheses of tetranuclear complexes (6)(7)(8)(9)(10) and simplified dinuclear complexes (11; 12), and single-molecule observation of the dinuclear complexes (13)(14)(15)(16) have been paid attention. However, the capacity of molecular QCA devices for molecular computing is still not clear.…”

Section: Introductionmentioning

confidence: 99%

Quantum-Chemical Design of Molecular Quantum-Dot Cellular Automata (QCA): A New Approach from Frontier Molecular Orbitals

Tokunaga¹

2011

Cellular Automata - Innovative Modelling for Science and Engineering

View full text Add to dashboard Cite

Scanning tunneling microscopy and spectroscopy investigations of QCA molecules

Cited by 25 publications

References 11 publications

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling

Scanning Tunneling Microscopy of Mixed Valence Dinuclear Organometallic Cations and Counterions on Au(111)

Quantum-Chemical Design of Molecular Quantum-Dot Cellular Automata (QCA): A New Approach from Frontier Molecular Orbitals

Contact Info

Product

Resources

About