Atomic Scale Data Storage Device by Means of Atomic Vacancy Manipulation

Abstract

The present invention is in the field of an atomic scale data storage device which uses vacancy manipulation, a method of providing said device, and a method of operating said device. Prior art mass data storage devices typically rely on magnetic materials forming discrete arrays or on nanoscale transistors. Further examples are e.g. optical systems such as a DVD and a compact disk. These devices and systems have a large, but for some applications still limited, storage capacity.

Claims

1-29. (canceled)

30. An atomic scale data storage device of at least one Mb comprising: a metallic single crystal surface, wherein the surface is stable at operating conditions; on the single crystal surface a two-dimensional lattice comprising positions in the lattice, which positions consist of non-metallic atoms representing a filled state or unfilled positions representing vacancies, wherein the metallic and non-metal atom are capable of forming a salt; a temperature regulator for maintaining a temperature; and a positioning device arranged to move non-metallic atoms over the two-dimensional lattice, wherein the single crystal surface and two-dimensional lattice are under a pressure of 10.sup.12-100 kPa.

31. The device according to claim 30, wherein the single crystal surface and two-dimensional lattice are under an inert gas atmosphere.

32. The device according to claim 30, wherein the metal is selected from elements of group 3-12, rows 4-6, and the non-metallic atoms are selected from elements of groups 13-17, rows 2-6.

33. The device according to claim 30, wherein the two-dimensional lattice comprises >50% filled positions.

34. The device according to claim 30, wherein the crystallographic lattice of the metal has at least one perpendicular symmetry element selected from a two-fold axis, a mirror, a four-fold axis, a three-fold axis, an inverse four-fold axis, a six-fold axis, and an inverse three-fold axis.

35. The device according to claim 30, wherein the metal is selected from Cu, V, Cr, Ni, Au, Ag, Pd, and Pt.

36. The device according to claim 30, wherein the non-metallic atoms are selected from halogens.

37. The device according to claim 30, wherein the metallic single crystal surface is provided on a substrate.

38. The device according to claim 37, wherein the metallic single crystal surface is provided on a substrate with at least one intermediate layer.

39. The device according to claim 30, wherein the crystal surface is a {100}, {110}, or {111} surface.

40. The device according to claim 30, comprising a cooler.

41. The device according to claim 30, wherein the two-dimensional lattice of halogen atoms comprises position markers for the positioning device.

42. The device according to claim 30, wherein the positioning device uses atomic force or electron tunnelling current for positioning, such as an AFM-type device or STM-type device.

43. The device according to claim 30, wherein the metallic single crystal surface has a defect density of less than 1/10.sup.4 nm.sup.2.

44. The device according to claim 30, comprising on the metallic lattice at least one interchangeable combination of a non-metallic atom and an on the lattice adjacent vacancy.

45. The device according to claim 30, comprising on the metallic lattice at least one region for storing non-metallic atoms for filling a vacancy on the lattice.

46. A method of providing a device according to claim 30, comprising the steps of: providing a crystalline metallic surface; optionally cleaning the crystalline metallic surface; and depositing non-metallic atoms on the surface.

47. A method of operating a device according to claim 30, comprising the steps of: providing the device; and writing data on the device by moving at least one non-metallic atom over the lattice from a first position to a second position.

Description

SUMMARY OF FIGURES

[0055] FIG. 1 shows a crystal lattice and positions thereon.

[0056] FIG. 2 shows movement of a non-metal atom.

[0057] FIG. 3a-c shows a bit convention.

[0058] FIG. 4 shows a partition of an atomic scale memory.

DETAILED DESCRIPTION OF FIGURES

[0059] FIG. 1 shows a crystal lattice and positions thereon. A crystallographic surface of metal atoms (M) is shown, in this case relating to a (100) surface. On the single crystal surface a two-dimensional lattice comprising positions in the lattice with non-metallic atoms (NM) representing a filled state and unfilled positions representing vacancies (AV) are visible. The two-dimensional lattice in this example relates to a so-called (22)R45 sub-lattice, as intermediate positions (IP) are not used for data storage; in other words only half of the available positions is used. The (22)R45 sub-lattice is indicated by a dashed line. The status of each position on the lattice may reflect a binary status wherein the non-metal may represent a (1) and the vacancy a (0), or vice versa. In an alternative approach, e.g. in view of shifting of the non-metal atom, a combination of two adjacent positions, indicated by a dotted line, may represent a binary status; the combination AV-NM may represent a (1), whereas the combination NM-AV may represent a (0), or vice versa; a consequence thereof is that the data density is half of the maximum density.

[0060] FIG. 2 shows an STM-image of movement of a non-metal atom. The non-metal atom, in casu a Cl-atom, is indicated with a circle. In four sequential steps it is moved one position to the right, one position downwards, one position to the left, and finally one position upwards, back to its original position. In the lower right a scale bar representing 1 nm is shown.

[0061] FIG. 3a shows an exemplary bit convention. Therein a first column is used, a second comprises non-metal atoms and contains no information, a third is used again, and so on. The top two rows are used for storing data, followed by a row comprising only non-metal atoms, which latter row can be regarded as a spatial division between two subsequent double rows for storing information; in other words, in a vertical direction the three rows shown can be repeated. The first bit indicated by a dashed line represent an AV-NM configuration, which configuration can be attributed with a binary 0. The next bit is a 1, and so on. An 8-bit configuration representing 01100101 is shown. In the figure some 5/6 (83.3% of the positions are filled (greyish area).

[0062] In FIGS. 3b and 3c a similar layout is shown as in FIG. 3a. Therein 75% and 50% of the positions are filled, respectively.

[0063] FIG. 4 shows a partition of an atomic scale memory. The black spots represent non-metal atoms, in casu Cl, on a metal surface, in casu Cu(100), whereas the regular white spots represent vacancies. A partition of the lattice into 8 by 10 sections is shown. Eight sections, indicated with dashed lines, are discarded for data storage. To mark such discarded sections, or likewise for other purposes, position markers are provided on the lattice, indicated with a circular dotted line. Each section comprises 8 horizontal positions, separated by a non-used position, and 8 vertical positions, separated by two positions, of which one position may be used to move the non-metal atom to.

[0064] The dashed-dotted section in the top-left corner indicates an 8 bits-array having 01001111 vertical bits (AV-NM etc.). Below each bit a NM Cl-atom is present forming a row of NM-atoms. Then, below the 8-bits array, a further 8 bits array is indicated (01101110), and so on.

[0065] Each section is separated by a small area, which is not used for data storage. These small areas may be used for position marking. In the present invention the position markers make use of 9 available positions; an X indicates a blocked section, whereas a \ indicates a section comprising data or available for storing data. A > and a V indicate the start and the end of a line, respectively. Examples thereof are indicated with dashed lines.

[0066] Adjacent to the sections, e.g. on the left, right, top and bottom side of the image, regions are available, e.g. for storing non-metal atoms.

[0067] On the top right side of the image a crystallographic imperfection is visible, which relates to a step between a first and second surface, the surfaces being at least one lattice constant apart.

[0068] The figures are further detailed in the description.

EXAMPLES/EXPERIMENTS

[0069] The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples and figures as detailed above. Details mentioned below relate to an article submitted for publication by Kalff et al., entitled A Kilobyte Rewritable Atomic Memory.

Experiment 1

[0070] A chlorinated copper surface is created in ultrahigh vacuum through the evaporation of anhydrous CuCl.sub.2 at 300 C. onto a clean Cu(100) crystal surface. The Cu crystal is pre-heated to 100-150 C. prior the CuCl.sub.2 deposition for about 12 minutes and kept at this temperature during the 210 s deposition and the 10 minutes post-anneal. This is found to result in formation of a square reconstruction of Cl atoms with a lattice constant of 0.36 nm. The Cl coverage (and thereby the vacancy coverage x) can be tuned by varying the duration of evaporation. For instance, an evaporation time of 240 s provides a vacancy coverage of 16.9%, whereas a time of 210 s gave 11.5% on the sample. Such can be determined by using an STM.

[0071] The obtained chlorinated surface is found to be resilient to tunnelling currents of up to 2 A when imaged at positive sample voltages of 200 mV or lower.

Experiment 2

[0072] Inventors moved vacancies by injecting a current of 1.00.5 A at a +500 mV sample voltage at a position close to a center of the vacancy to a center of a neighboring Cl atom at the desired location. The STM feedback was kept switched on throughout the manipulation procedure. It was found that a directional reliability (i.e. how often a vacancy moves in the desired direction once it moves) is in excess of 99%. Controlled vacancy movement is at present limited to the (1,0) and (0,1) directions on the two dimensional lattice.

Experiment 3

[0073] In this experiment the present inventors used only a part of the two dimensional lattice. In the lattice a vertical pair of a chlorine atom (Cl, or NM) and an adjacent vacancy (AV) were defined as a bit, wherein the AV-Cl configuration represents the 0 and Cl-AV the 1. In order to avoid vacancies directly neighbouring each other, which could render automated locking of the STM tip on individual vacancies impossible, inventors implemented a row of Cl (NM) atoms to separate bits in both the horizontal and vertical directions. For this reason, 6 lattice sites are needed for a bit, and likewise 48 lattice sites for a byte, resulting in an optimal vacancy coverage 16.7%.

Experiment 4

[0074] Inventors made use of an automated manipulation device that resulted in construction of large numbers of data. A marker at the top left of each block was used to define a scan frame and a lattice for a complete block. After scanning an area, the positions of all vacancies were determined through image recognition. Next, a pathfinding algorithm was used to calculate a positioning sequence, guiding the vacancies to their respective final positions. In addition markers for adjacent blocks were built automatically as part of the construction and leftover vacancies are swept to a side to be used in optional future blocks. Automated construction of a complete block took in the order of 10 minutes.