| 研究課題/領域番号 |
19K05204
|
|---|
| 研究機関 | 北陸先端科学技術大学院大学 |
|---|
研究代表者 |
フロランス アントワーヌ 北陸先端科学技術大学院大学, 先端科学技術研究科, 講師 (30628821)
|
|---|
| 研究期間 (年度) |
2019-04-01 – 2022-03-31
|
| キーワード | Silicene |
|---|
| 研究実績の概要 |
In FY2020, the possibility of dissolving zirconium diboride (ZrB2) with phosphoric acid (H3PO4) and sulfuric acid (H2SO4) was verified and the conditions (concentration, time) required for fully etching ZrB2 thin films on Si(111) were determined. We demonstrated that it is not possible to etch selectively ZrB2 when it is covered with an inert h-BN single layer: The h-BN prevents the dissolution of ZrB2 and gets etched instead. This suggests that the formation of free-standing silicene requires an etching of the ZrB2 thin film from the side. For this purpose, I learned how to use the electron beam lithography apparatus which will be used to pattern stripes in ZrB2 thin films on Si(111).
An other route was considered for transfering h-BN/silicene bilayers from ZrB2 thin films. This method consists of (1) growing h-BN/silicene/ZrB2 sandwiches on a silicon on oxide (SOI) substrate, and then (2) etching the oxide layer to obtain a silicon membrane topped by a ZrB2/silicene/h-BN sandwich. (3) Etching the silicon layer and (4) etching the ZrB2 thin film from the back or from the side. ZrB2 thin films could be grown on SOI using a method slightly different from that used for the growth on Si(111) substratess to preserve a sharp frontier between the oxide and top Si(111) layer. The possibility of forming a silicene layer on top of the ZrB2 thin film was verified together with the feasibility of transferring the top silicon layer to a teflon adhesive tape by dissolving the oxide layer in concentrated hydrofluoric acid (HF).
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The project progressed satisfactorily during FY2020. Experiments provided insightful indications on the feasibility of the different methods considered and give clear directions for the last year of the project.
|
| 今後の研究の推進方策 |
The last year of the project will focus on two different possible methods to realize an encapsulated free-standing-like form of silicene.
The first one involves e-beam lithography. Stripe-shaped islands will be patterned in ZrB2 thin films grown on Si(111). h-BN thin film will then be grown by nitridation and annealing selectively on top these stripes leaving their sides exposed. A subsequent silicon deposition will give rise to silicene stripes protected by h-BN layers. Immersing the samples in acid etchant is expected to disolve ZrB2 thin film much faster than the h-BN and silicene layers. The etching will thus give rise to encapsulated free-standing silicene stripes.
The second objective for the last year of the project is to address the exfoliation of h-BN/silicene bilayers from ZrB2 thin films grown on SOI. The possibility of growing h-BN/silicene/ZrB2 sandwiches on SOI will first be verified. The transfer of the h-BN/silicene/ZrB2 sandwiches to a teflon tape without damages through the etching of the oxide layer by HF and the silicon layer with a silicon etchant (like potassium hydroxide) will be determined. The etching of the ZrB2 thin film and their transfer to an insulating substrate will be attempted.
These experiments will combine growth techniques in ultra high vacuum with electron beam lithography and chemical etchings. Some steps requiring an inert atmosphere will be done in a glove box. Characterizations will involve scanning tunneling microscopy, optical microscopy, atomic force microscopy and electron microscopy.
|
| 次年度使用額が生じた理由 |
The money which could not be used for travelling due to the restrictions related to the COVID-19 epidemy, will be used to hire research assistants. Additional manpower will increase the chances of success of this project.
|
