| 研究実績の概要 |
Important steps towards the exfoliation of h-BN-encapsulated silicene were achieved during the last year. Methods for patterning zirconium diboride (ZrB2) thin films by means of e-beam lithography and wet etching, was conducted in order to create patterned h-BN-encapsulated silicene sheet that can then be exfoliated.
200 nm-wide stripes with different length were patterned in a positive photoresist in order to be replicated in the ZrB2 thin film through etching with concentrated solutions of phosphoric acid.
Efforts were also dedicated to obtaining free-standing-like ZrB2 thin films. The method which was found to be the most suitable, is the chemical etching of the oxide layer of silicon-on-oxide (SOI) substrate that releases the thin Si membrane on which a ZrB2 thin film was grown. Whereas the possibility of removing the Si membrane was already verified, methods to preserve the ZrB2 thin film from been etched by the highly corrosive hydrofluoric acid used to etched the oxide layer, still need to be determined.
Additionnaly, a process to transfer ZrB2 thin films from SOI substrate to a flexible substrate such as a teflon tape was established. In particular an adhesive tape which can resist the immersion in the etchant and can be dissolved in an usual solvant such as acetone. The preservation of the cleaness of the ZrB2 surface through the process, crucial for the growth of encapsulated silicene, was verified.
The wet etching of the silicon membrane, required to release the h-BN-encapsulated silicene on ZrB2, using the usual KOH etchant was attempted but without success.
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| 今後の研究の推進方策 |
The following year will be dedicated to the completion of the project. Methods for exfoliating the silicon membrane from the SOI substrate without etching the ZrB2 will be investigated: The passivation of the ZrB2 thin film by a polymer layer and keeping the silicon-on-oxide floating at the surface of the etching solution.
The patterning of ZrB2 thin film will be optimized. Other etching methods such as reactive ion etching will be attempted to obtain sharp edges.
Different techniques will be tried in order to remove the silicon membrane after its exfoliation from the SOI substrate.
After fixing the system used to grow h-BN, h-BN-encapsulated silicene will be prepared on zirconium diboride thin film grown on SOI and on patterned ZrB2 thin films. Then the possibility of etching the ZrB2 thin film to create a free-standing-like h-BN-encapsulated silicene, will be attempted.
Following the methods established last year, the transfer of h-BN-encapsulated silicene on ZrB2 from SOI substrate to a flexible substrate will also be tried.
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| 次年度使用額が生じた理由 |
The money will be used to pay consumables such as high purity nitrogen gas, substrates, chemicals etchants and solvents.
If possible, research asistants will be hired.
Various equipment, which appeared to be necessary such as a dessicator, heating ultrasonic bath, twizzers or glassware will also be purchased.
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