Dynamic information storage or retrieval – Specific detail of information handling portion of system – Electrical modification or sensing of storage medium
Reexamination Certificate
2000-12-01
2003-01-14
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Electrical modification or sensing of storage medium
C369S047100, C250S306000
Reexamination Certificate
active
06507552
ABSTRACT:
FIELDS OF THE INVENTION
The present invention relates to a data storage device capable of storing, reading and writing data to data storage areas of nanometer dimensions.
BACKGROUND OF THE INVENTION
Recently, scientists have been developing alternative ultra-high-density data storage devices and techniques useful for operating ultra-high-density data storage devices. These devices and techniques store data bits within storage areas sized on the nanometer scale and possess advantages over conventional data storage devices. Among these advantages are quicker access to the data bits, a lower cost per bit and enablement of the manufacturing of smaller electronic devices.
FIG. 1
illustrates an ultra-high-density data storage device configuration according to the related art that includes a storage medium
40
that is separated into many storage areas (illustrated as squares on the storage medium
40
), each capable of storing one data bit. Two types of storage areas, unmodified regions
140
that typically store data bits representing the value “0” and modified regions
130
that typically store data bits representing the value “1”, are illustrated in FIG.
1
. Typical periodicities between any two storage areas in these devices range between 1 and 100 nanometers.
FIG. 1
also shows, conceptually, emitters
350
positioned above the storage medium
40
, and a gap between the emitters
350
and the storage medium
40
. The emitters
350
are capable of emitting electron beams and are arranged on a movable emitter array support
360
(also known as a “micromover”) that can hold hundreds or even thousands of emitters
350
in a parallel configuration. The emitter array support
360
provides electrical connections to each emitter
350
as illustrated conceptually by the wires on the top surface of emitter array support
360
.
The emitter array support
360
can move the emitters
350
with respect to the storage medium
40
, thereby allowing each emitter
350
to scan across many storage areas on the storage medium
40
. In the latter case, the storage medium
40
can be placed on a platform that moves the storage medium
40
relative to the emitter array support
360
. The platform can be actuated electrostatically, magnetically or by the use of piezoelectrics and, dependent upon the range of motion between the emitter array support
360
relative to the storage medium
40
, each emitter
350
can have access to data bits in tens of thousands or even millions of data storage areas.
Related Art: (Ultra-High Density Data Storage Devices)
Some specific embodiments of the ultra-high-density data storage device discussed above are disclosed in U.S. Pat. No. 5,557,596 to Gibson et al. (Gibson '596), the contents of which are incorporated herein in their entirety by reference.
The devices disclosed in the Gibson '596 patent include a storage medium
40
with modified regions
130
and unmodified regions
140
, emitters
350
and an emitter array support
360
. The Gibson '596 devices provide a relatively inexpensive and convenient method for producing ultra-high-density data storage devices that can be manufactured by well-established and readily-available semiconductor processing technology and techniques. Further, some of the devices disclosed in the Gibson '596 patent are somewhat insensitive to emitter noise and variations in the gap distance between the emitters
350
and the storage medium
40
that may occur when the emitters
350
move relative to the storage medium
40
during device operation. Reasons for these insentivities are related, for example, to the nature of the diode devices disclosed in the Gibson '596 because the diodes allow constant current sources to be connected to the emitters
350
and allow the electron beam energy to be monitored independently of the signal current in order to normalize the signal as described in the Gibson '596 patent. However, the devices disclosed in the Gibson '596 patent must be operated under stringent vacuum conditions.
The storage medium
40
, according to the Gibson '596 patent, can be implemented in several forms. For example, the storage medium
40
can be based on diodes such as p-n junctions or Schottky barriers. Further, the storage medium
40
can include combinations of a photodiode and a fluorescent layer such as zinc oxide. This type of configuration relies on monitoring changes in the cathodoluminescence of the storage medium
40
to detect the state of a written bit. Also, according to the Gibson '596 patent, the storage medium
40
can be held at a different potential than the emitters
350
in order to accelerate or decelerate electrons emanating from the emitters
350
.
The emitters
350
disclosed in the Gibson '596 patent are electron-emitting field emitters made by semiconductor micro-fabrication techniques and emit very narrow electron beams. These can be silicon field emitters but can also be Spindt emitters that typically include molybdenum cone emitters, corresponding gates and a pre-selected potential difference applied between each emitter and its corresponding gate. The Gibson '596 patent also discloses electrostatic deflectors that sometimes are used to deflect the electron beams coming from the emitters
350
.
According to the Gibson '596 patent, the emitter array support
360
can include a 100×100 emitter
350
array with an emitter
350
pitch of 50 micrometers in both the X- and Y-directions. The emitter array support
360
, like the emitters
350
, can be manufactured by standard, cost-effective, semiconductor micro-fabrication techniques. Further, since the range of movement of the emitter array support
360
can be as much as 50 micrometers, each emitter
350
can be positioned over any of tens of thousands to hundreds of millions of storage areas. Also, the emitter array support
360
can address all of the emitters
350
simultaneously or can address them in a multiplex manner.
During operation, the emitters
350
are scanned over many storage areas by the emitter array support
360
and, once over a desired storage area, an emitter
350
can be operated to bombard the storage area with either a high-power-density electron beam or a low-power-density electron beam. As the gap between the emitters
350
and the storage medium
40
widens, the spot size of the electron beams also tends to widen. However, the emitters
350
must produce electron beams narrow enough to interact with a single storage area. Therefore, it is sometimes necessary to incorporate electron optics, often requiring more complicated and expensive manufacturing techniques to focus the electron beams.
If the emitters
350
bombard the storage areas with electron beams of sufficient power density, the beams effectively write to the storage medium
40
and change the bombarded storage areas from unmodified areas
140
to modified areas
130
. This writing occurs when electrons from the high-power-density-electron beams bombard the storage areas and cause the bombarded storage areas to experience changes of state such as changes from crystalline structures to amorphous structures or from undamaged to thermally damaged.
The changes of state can be caused by the bombarding electrons themselves, specifically when collisions between the electrons and the media atoms re-arranges the atoms, but can also be caused by the high-power-density-electron beams transferring the energy of the electrons to the storage areas and causing localized heating. For phase changes between crystalline and amorphous states, if the heating is followed by a rapid cooling process, an amorphous state is achieved. Conversely, an amorphous state can be rendered crystalline by heating the bombarded storage areas enough to anneal them.
The above writing process is preferable when the storage medium
40
chosen contains storage areas that can change between a crystalline and amorphous structure and where the change causes associated changes in the material's properties. For example, properties such as
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