New Nanomaterials that Might Change the Chips Industry

Nanomaterials refer to materials whose dimensions reach the nanometer scale in one-dimensional, two-dimensional or three-dimensional direction. It can be divided into zero-dimensional materials, one-dimensional materials, two-dimensional materials, and three-dimensional materials. When a conventional material reaches the nanometer scale, its properties will be greatly different from usual.

When the nanomaterial has the thickness of a single atom, it is called two-dimensional material. Graphite, which was discovered in 2004, is the representative of this particular type of materials. In recent years, transition metal two-dimensional materials have caught great attentions from scientists. For instance, tungsten disulfide, molybdenum disulfide or tungsten diselide, which have great application potential for the next generation of electronic products.

Two-dimensional transition metal disulfide (TMD) is expected to be used in next generation of electronic and optoelectronic applications. However, in order to fully exploit the potential of these semiconductors. Researchers need to fabricate extremely thin wires from these materials as to use them as atomic contacts. These nanowire require a material that is even smaller and thinner than two-dimensional material. They are what called one-dimensional materials.

Two-dimensional materials refer to materials in which electrons can move freely on a non-nano scale in two dimensions, while one-dimensional materials can only move in only one dimension. The major forms of such materials are nanowires, nanorods, nanotubes, etc. It must be pointed out that, there is currently no economically viable production process for graphene, tungsten disulfide (molybdenum) or any other two-dimensional, one-dimensional materials.

Recently, a scientific team at Cornell University in New York has adopted a new "dislocation catalysis" technology to successfully embed a one-dimensional molybdenum sulfide channel in a two-dimensional tungsten selenide monolayer. Finally, the edge of the one-dimensional channel has no mismatch misalignment and dangling bonds, so this technique can be easily extended to other 2D materials such as tungsten diselenide and molybdenum disulfide.

For the details of the study, the scientists said: "Reducing the thickness of the atomic layer. The width of the two-dimensional material is crucial for the future of such materials, to break through the existing position that the chips industry is based on silicon wafer. Reducing the size of existing chips to a few nanometers is of great significance for semiconductor expansion of future chips, and it is conceivable that chips that can be implanted into the human body, or more intelligent computer facilities or robots.”

Previously, researchers have produced a 2D heterostructure device by lithographically patterning a 2D layer of one material and then growing another layer of 2D material on top of the first layer in the patterned region. Although this technique can restrict the size of materials to around 100 nanometers, the lithographic patterning process itself produces atomic defects and contamination. The atomic junctions in these heterostructures contain electron-defective states that adversely affect the final electronic properties of the device.

Thus, the research team proposed a new method to create a consistent one-dimensional channel in a two-dimensional heterostructure. Firstly they made a lateral interface between the two two-dimensional transition metal dichalcogen materials, molybdenum disulfide (MoS2) and tungsten disilicide (WSe2). The precursor molecules are then introduced into the bulk to provide a high chemical potential for the channel material, one-dimensional molybdenum disulfide nanowires (MoS2). The core of misfit dislocations is more reactive than its surroundings, which allows channel atoms (Mo and S) to be inserted into the dislocation core. This pushes the dislocations away from the original interface between MoS2 and WSe2, and the process creates a one-dimensional MoS2 channel in the trajectory behind the core.

These channels are less than 2 nm wide and have no dislocations and dangling bonds on the sidewalls. This technique, called "dislocation catalysis", was explained by the researchers: "This misaligned catalytic growth technique is like replacing a white silk with a red silk sheet. More vividly, because of the connection of semiconductor one-dimensional nanowires, the exchange channel between two-dimensional semiconductor materials has changed from a small intestine path to a high-speed railway. This process will play a vital role in semiconductor nanoscience ."

Finally, scientists also believe that, based on their density functional calculations, one-dimensional molybdenum disulfide (MoS2) wires have extraordinary electronic properties that can be applied, such as quantum confinement and type II tape alignment, and they hope to use two-dimensional materials. They are patterned and these patterned 2D materials are stacked to create highly integrated flexible and transparent circuits that are useful for future development of new computer devices.

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