This work is supported by the National Institute of Standards and Technology of the United States Department of Commerce.

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The authors declare no competing financial interests. Commercial materials, instruments and equipment are identified in this paper to specify the experimental procedure as completely as possible. In no case does such identification imply a recommendation or endorsement by the National Institute of Standards.

적절한 구성과 구조를 확인하기 위해 특징으로 고품질의 대량 샘플의 취득 후, 샘플은 1cm 기판의 × 1cm 조각에 샘플 조각을 엑스 폴리 에이 팅에 의해 묘사 된 형상으로 패터닝된다. 그들은 백 게이트의 적용을 허용함으로써 실험적 파라미터 공간을 증가로서 SiO2를 약 300nm의 적용 무겁게 p- 도핑 된 Si로 이루어지는 기판이 바람직하다. 샘플은 충분히 얇아 야 - 미만 10 내지 - 튜닝에 충분한 전계 효과 홀바 장치의 전도 채널의 전체 화학적 전위를 생성한다. 샘플 두께는 적절히 다이 싱 테이프 기준 웨이퍼를 사용하여 벌크 재료 조각을 박리 반복 플레이크 계획된 실험의 목적을 위해 충분한 두께까지 신선한 테이프로 부착 조각으로 테이프를 가압에 의해 제어된다. 조각을 기판에 전사 샘플을보고 너무 작아서육안 때문에 광학 현미경 홀 막대기로 제조하기에 적합한 전사 부분을 식별하기 위해 이용되어야한다. 샘플 플레이크 두께를 정확하게 원자력 현미경 (AFM)을 사용하여 측정하고, 충분한 경험하지만 연구자 플레이크의 색에 기초하여 원하는 두께의 샘플을 식별 할 수있다. 샘플 조각 적절히 반 데르 발스 힘에 의해 조각을 기판과 접합하지 않는 경우,이 원고에 기재된 기술적 절차에 띄는 문제는 발생한다. 이 경우, 제조 과정의 단계들의 임의의 수 중 (특히 용매 중에 침지) 표본 플레이크 노크 될 또는 기판 표면의 부분 씻어. 이는 샘플 플레이크가 SiO2를 스퍼터링의 조각을 코팅함으로써, 기판 부분에 고정되어있다이 원고에 기재된 신규 한 방법에 의해 해결된다. 이 작업이 완료되면, 샘플 플레이크의 일부는 직접 노출 할 수 있도록해야금속 접촉부의 dherence. 이러한 콘택트의 증착에 사용되는 마스크는이 샘플에 전기적 접촉을 허용하는, 금속 접촉이 증착 될 정확히 SiO2를 에칭하는 것처럼, SiO2를 에칭하기위한 마스크로서 작용하여 이러한 목적에 맞게 사용될 수있다 플레이크는 여전히 지역의 대부분에 걸쳐 스퍼터링의 SiO2로 고정 플레이크를 유지하면서. 탐색 재료 과학 연구의 추구의 일환으로 여러 가지 새로운 물질 운송 연구를 허용 벌크 물질의 종래의 전송 측정에 충분한 크기의 결정으로 합성 된 신규 한 벌크 재료의 이송 측정이 단계 허용 수행. 이 문서에 설명 된 실험 기법에 의해 제공 심오한 기술 발전은 헤테로 구조에 여러 레이어 소재를 스택 할 수있는 능력에서 온다. 이것은 많은 장점을 가지고있다. 육각형 질화 붕소 (HBN) 일 수있다담체 상태의보다 정확한, 무 결함 전송 측정을 허용 이러한 그래 핀과 같은 다른 재료 2D, 공기와의 상호 작용으로부터 발생하는 결함이 제품 표면을 끼우도록 사용된다. 또한, 흥미로운 긴급 행동은 다른 재료 (12)의 스택 형성 헤테로 구조에서 관찰 할 수있다. 각질 제거 후, ​​조각, 적합한 샘플 조각의 식별을 기판에 전달, 절차는 고분자 폴리 디메틸 실록산 (PDMA) 및 폴리 프로필렌 카보네이트 (PPC)의주의를 이용하여 샘​​플 전송을 포함하는 다층 재료의 헤테로 스택을 생산하기 위해 따라 할 수있다. 적층 함께 적층 재료의 깨끗한 표면을 누름으로써 발생하는이 방법은, 인접하는 재료들 사이의 오염 물질로서 이들 중합체의 구체를 도입하지 않고 이러한 적층을 허용한다. 완성 된 헤테로 스택은 장치 제조를위한 새로운 기판 부재에 전달 될 수있다. 장치 FABRI양이온은 많은 단계를 포함하는 엄격한 과정이다. 적당한 샘플 조각이 전송 식별하고되면 필요한 경우, 여러 개의 개별적인 조각으로 구성된 헤테로 구조로 적층 된, 고분자 마스크 응용 패터닝 및 제조 공정에 관련된 에칭 및 금속 증착을 여러 번 반복하는 단계는 몇 취할 수 일는 고품질 단일 샘플을 생성한다. 인해 원하는 크기, 두께 및 품질의 박편 부분이 식별 된 후에 결정될 수 있어야 기판 편과 홀 바 차원 어디서나 볼 수있다이 방법의 발견 및 프로브 특성, 리소그래피 이루어져야 전자선 묘화에 의한. 전자선 리소그래피는 전자 빔의 포커싱 된 주사의 사용을 통한 약 5 nm의 치수까지 구조물의 직접 쓰기를 허용 고급 리소그래피 기술이다. 특정 장치 구조는 각 샘플에 대해 준비된다. 등방성 에칭은 플라즈마 유전자를 사용하여 수행반응성 이온 에칭 (RIE) 방식으로 평가. 육각형 질화 붕소 / 그래 핀 / 육방 정 질화 붕소 스택의 에칭이 플라즈마 에칭에 사용되는 기체는 O 2 CHF (3)의 혼합물이다. 용착 금속 접촉은 전자 빔 증착 실에서 고진공 접착층, 및 높은 전기 전도도를 위해 선택의 Au 750 nm 인 제 2 층, 증착에 순차적으로 제공하는 것을 의미 CR의 얇은 층으로 구성. 디바이스의 제조는, 성공적인 금속 리프트 오프 다음 금속 증착이 완료된 후 이후 디바이스가 패키지에 결합 실험 측정 magnetotransport의 저온 유지 장치로로드 될 수있다 가리. 이 논문에 기재된 제조 및 실험 기술의 발전은 개인 플레이크 헤테로 구조로 적층 될 수있는 절차의 개선을 포함한다. 또한, 각각의 조각과 적층 재료의 적층의 박리이 논문에서 설명 된 기술들에 의해 헤테로 공기에 노출시켜 달성하지 재료에 한정된다. 추가적인 고려는, 예컨대 불활성 환경에서의 절차의 많은 착수로서는, 천이 금속과 dichalcogenides 비스무트 칼 코겐 위상 절연체로서 산화에 의해 파괴되는 물질에 대해 취해 져야한다. Magnetotransport 시스템은 강력한 자석과 낮은 온도의 저온 유지 장치가 설계 될 때 더 강력한 실험 측정 기능에지도 개선을 볼 것입니다.

첨단 전자 기술 재료 플랫폼의 추구는 높은 처리량 재료 합성 및 후속 특성에 대한 방법을 요구한다. 이 추구 관심 신규 물질은 분자 빔 에피 택시 또는 더 복잡한 단결정 박막 형성 기술보다 더 빠른 방식으로 직접 반응 합성 1,2-, 전기 화학적 성장, 4, 및 기타 방법 (5)에 의해 대량으로 제조 할 수있다 화학 증착법. 벌크 크리스탈 샘플의 전송 특성을 측정하는 종래의 방법은 약 1mm X 1mm X 6mm의 치수를 갖는 직육면체 형상의 조각을 절단하고 와이어 홀 바 구성 6 샘플에 이르게 부착하는 것이다. 기존의 벌크 홀바 디바이스의 제조 방법은, 시료의 측정에 대한 전송 측정 가능한 장치를 제조하기에 충분 상기 특정 재료는 도전을 제기. 이있을 수있다원하는 샘플 두께는 단지 몇 개의 단일 층에 하나의 순서, 또는 때문에 생산 결정에도 강력한 광학 현미경에 리드선을 부착 너무 작아 발생할 한 층상 이차원의 스택을 측정하는 것을 목적으로하기 때문에 근 또는 서브 나노 미터 두께의 재료. 첫 번째 범주는 예를 들어 나노 와이어로 구성하고, 산화 몰리브덴의 특정 제제는 7 청동. 두 번째 범주는 그래 핀 (8)과 같은 두 가지 차원 물질의 단일 매우-몇 개의 층으로 이루어져있다, TMDS (MOS 2, WTE 2 등), 및 위상 절연체 (BI 2 SE 3은, 양성애자는 Sb로 1-X 테 (3) X 등). 세 번째 범주는 계층 전송, HBN-그래 핀 HBN 9 특히 중층 스택을 통해 수동 조립하여 두 차원 재료의 각 층을 적층하여 제조 된 헤테로 구조로 구성되어 있습니다. 새로운 전자의 탐색 적 연구lectronic 재료 어려운 샘플들에 측정 장치를 제조하기위한 적절한 방법을 요구한다. 종종, 직접 반응 또는 전기 화학적 성장에 의해 합성 된 새로운 물질의 첫 번째 배치는 마이크론의 크기 순서에 치수가 매우 작은 단결정을 얻을 수 있습니다. 이러한 샘플은 역사적으로 새로운 물질의 높은 처리량 연구 장애물 프리젠 쉽게 운송 장치의 제조를 위해 더 큰 결정을 달성하기 위해 샘플 성장 파라미터의 향상을 필요로 금속 접촉부를 연결하는 거대 어려운 입증. 물질의 신속한 특성화를 가능하게하기 위해, 매우 작은 샘플 장치의 제조 방법은 즉시 예비 일괄 제작 되었기 때문에 신규 한 물질의 특성을 허용하기 위해 고안되었다. 이 방법의 약간의 변화는, 그러한 그라, HBN 및 TMDS 같은 이차원 물질 샘플을 사용하여 박리 된 장치뿐만 아니라 MA의 다층 헤테로 구조의 제조에 적용 할 수있다terials. 장치가 부착 및 상용 초전도 자석, 건조 헬륨 근접주기 그라 이오 스탯 magnetotransport 시스템에 삽입 패키지에 와이어 본딩. 전송 측정은 T. (12)까지 0.300 K 아래로 온도와 자기장에서 촬영

<table border="0" cellpadding="0" cellspacing="0" width="840">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Cryogenic Limited 12T CFMS</td>
			<td style="width:89px;">Cryogen Limited</td>
			<td style="width:135px;">CFM-12T-H3- IVTI-25</td>
			<td style="width:417px;">Magnetotransport system customized with modulated field magnet (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">7270 DSP Lock-in amplifier</td>
			<td style="width:89px;">Signal Recovery</td>
			<td style="width:135px;">7270</td>
			<td style="width:417px;">lock-in amplifier for source/drain and voltage measurements (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">GS200 DC Voltage/Current Source</td>
			<td style="width:89px;">Yokogawa</td>
			<td style="width:135px;">GS200</td>
			<td style="width:417px;">Voltage source for gate voltage application (step 4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">2636B System Sourcemeter</td>
			<td style="width:89px;">Keithley</td>
			<td style="width:135px;">2636B</td>
			<td style="width:417px;">Sourcemeter for source/drain and voltage measurements</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">DWL 2000 Laser Pattern Generator</td>
			<td style="width:89px;">Heidelberg Instruments</td>
			<td style="width:135px;">DWL 2000</td>
			<td style="width:417px;">Generate chrome mask for lithography of substrate location/alignment feature pattern (step 1.3)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Suss MicroTec MA6/BA6 Contact Aligner</td>
			<td style="width:89px;">Suss</td>
			<td style="width:135px;">MA6</td>
			<td style="width:417px;">Used for the lithography of substrate location/alignment feature pattern (step 1.4.12)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">JEOL Direct Write Electron Beam Lithography System</td>
			<td style="width:89px;">JEOL</td>
			<td style="width:135px;">JBX 6300-FS&#160;</td>
			<td style="width:417px;">Perform high-resolution lithography of devices</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Discovery 550 Sputtering System</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Discovery 550</td>
			<td style="width:417px;">Perform SiO2 sputtering (step 2.5)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Infinity 22 Electron Beam Evaporator</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Infinty 22</td>
			<td style="width:417px;">Perform Cr/Au deposition (steps 1.5 and 3.7)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Unaxis 790 Reactive Ion Etcher</td>
			<td style="width:89px;">Unaxis</td>
			<td style="width:135px;">Unaxis 790</td>
			<td style="width:417px;">Etch sample into Hall bar structure (step 3.4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">Name</td>
			<td style="width:89px;">Company</td>
			<td style="width:135px;">Catalog Number</td>
			<td style="width:417px;">Comments</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 495 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 495 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for lithography (step 3.5.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 950 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 950 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for sample dicing and lithography (steps 1.7.3, 3.3.1, and 3.5.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">S1813 positive photoresist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">S1813 G2</td>
			<td style="width:417px;">Positive photoresist (step 1.4.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">LOR resist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">LOR 3A</td>
			<td style="width:417px;">Lift off resist (step 1.4.3)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1:3 MIBK:IPA PMMA developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">1:3 MIBK:IPA</td>
			<td style="width:417px;">PMMA developer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">MF-321 Developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">MF-321</td>
			<td style="width:417px;">Novolac positive photoresist-compatible developer solution (step 1.4.15)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Diglycidiyl ether-terminated polydimethylsiloxane</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 480282</td>
			<td style="width:417px;">For layered material stacking (step 2.6.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Polypropylene carbonate</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 389021</td>
			<td style="width:417px;">For layered material stacking (step 2.6.2)</td>
		</tr>
	</tbody>
</table>

advanced experimental methods for low-temperature magnetotransport measurement of novel materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

도 3은 저온 magnetotransport 실험 목적 패터닝 전형적인 홀바 장치를 도시한다. 위 그림의 광학 이미지는 성공적으로 제작 된 그래 핀 / HBN 홀 막대를 보여줍니다; 하부 이미지 랜도 레벨 (LLS)에서 발생 론 도어-Büttiker 에지 상태를 갖는 장치 개략적 인 양자화 홀 저항의 값을 계산하는데 사용될 수있는 전송 메카니즘으로 설명 될 것이다의 실험적 조사를 도시 이 문서에 설명 된 실험 기술의 대표적인 응용 프로그램입니다. 종종, 홀 바 구조의 제조는 전체 제조 공정에서 상당한 도전을 구성한다. 이 형상으로 샘플을 에칭하는 단계는 생략 될 수 있고, 리드는 그들이 기판에 전사 부재를 다음과 같이 조각 샘플에 직접 부착 될 수있다. 그러나, 불완전한 형상은 차를 허용하지 않습니다그래서 홀 바 구조로 샘플을 에칭하는 단계를 건너 뛰는 수송 특성의 eful 측정, 초기 측정을 제한해야한다. 실험적인 매개 변수는 연관된 AC 종속 전압 측정과 잠금 증폭기로부터 발진기에 의해 공급 될 수있다 (30) V. 교류 전류만큼 높은 12 T만큼 높은 자기장 0.300 K의 낮은 온도, 및 게이트 전압을 포함 직류는 연관된 DC 전압 측정과 소스 미터에 의해 공급 될 수있다. 및 직류 전류의 크기에 비해 교류 것은 검토되고 물질의 조심스럽게 파괴 저항 특성을 비롯한 특성에 기초하여 선택되어야 파라미터이다. 홀 저항 사이의 전위 차이로 정의되며, 또는 전체 측정 된 전압은,인가되는 전류에 의해 분할도 3에서 6, 2 리드. 세로 재sistance 간의 전위차로 정의되고, 또는 전압에 걸쳐 측정 된, 2 및 3이인가되는 전류로 나눈 리드. 완전히 그래 핀을 캡슐화 HBN 플레이크에 의해 보호 상단 표면에 그래 핀 홀 바에서 측정에서 -30 V 30 V. 그림 4에 이르기까지 T에서 -6 T 6에 이르기까지 자기장 다시 게이트 전압에서 1.7 K 홀 저항이 매개 변수 공간 내에서 변경하는 방법을 보여줍니다. 그래 핀 / HBN 홀 바, 랜도 레벨 충전 대응 홀 저항 구체적 관찰 고원 측정 홀 저항의 동작은, 양자 홀 효과의 모델 예를 들어, 그러한의인가에 의해 관찰 양자 역학적 현상 이 문서에 설명 된대로 고급 magnetotransport 기술. 도 5는 홀 저항, B = T (6)에서도 4에 제시된 데이터의 슬라이스를 나타낸다 (R의 XY) 백 게이트 전압의 함수로서 백 게이트 전압의 함수와 대응하는 종 방향의 저항 (R의 XX) 등. 측정은 명확하게 그라 핀은 정수 값 랜도 수준의 수 (n), 플랑크 상수 h를, 및 전자 무료 전자와의 양자화 된 홀 저항 값을 갖는 양자 홀 효과를 발휘 보여줍니다. 양자화 된 홀 저항 고원 종 저항을 소멸과 일치한다. <img alt="그림 1" src="/files/ftp_upload/53506/53506fig1.jpg" /> 1. 기판 패턴을 그림. (A) 샘플 기판의 리소그래피 패터닝 위치 / 정렬 마크에 대한 설계 구성의 영역. 패턴 금 위치 / 정렬 마크의 (B) 컴퓨터 렌더링. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig1large.jpg" target="_blank">더 큰 버전을 보려면 여기를 클릭하십시오</a><html> 이 그림의. <img alt="그림 2" src="/files/ftp_upload/53506/53506fig2.jpg" /> 그림 2. 그래 핀 플레이크. 광학 현미경을 통해 관찰 CR / 금 위치 마커에 인접한 단일 층 그래 핀 플레이크의 이미지입니다. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig2large.jpg" target="_blank">이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오.</a> <img alt="그림 3" src="/files/ftp_upload/53506/53506fig3.jpg" /> 그림 3. 홀 바 장치. 위 그림, 금속과 그래 핀 / HBN 홀 바 장치의 광학 이미지는 단말기에 접촉 리드. 낮은 그림, 장치의 광학 이미지의 숫자로 표시된 단자에 해당하는 번호가 연락처 리드 장치의 개략도. 화살표는 현재 발생 론 도어 - Büttiker 에지 상태의 흐름을 보여줍니다.ES / ftp_upload / 53506 / 53506fig3large.jpg &quot;대상 =&quot;_ 빈 &quot;&gt;이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오. <img alt="그림 4" src="/files/ftp_upload/53506/53506fig4.jpg" /> 자기장 및 글로벌 백 게이트의 함수로 홀 저항 그림 4. 3D 플롯. 1.7 K는 양자 전송 동작을 시연에서 자기장 및 글로벌 다시 게이트의 기능과 양자 홀 정권에서 그래 핀 홀 바의 홀 저항의 3D 플롯. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig4large.jpg" target="_blank">이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오.</a> <img alt="그림 5" src="/files/ftp_upload/53506/53506fig5.jpg" /> 그림 5. 홀과 종 자기. 홀 (R의 XY)와 종 (R의 XX) 수정의 글로벌 다시 게이트의 기능과 저항ED 자기장 │B│ 종 저항을 소멸과 일치 양자화 홀 저항 값과 양자 홀 효과를 입증 = 6 T. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53506/53506fig5large.jpg" target="_blank">이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오.</a>

Watch this Scientific Journal Video about Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials at JoVE.com

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

소설 재료의 저온 Magnetotransport 측정을위한 고급 실험 방법

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

advanced-experimental-methods-for-low-temperature-magnetotransport

Nanyang Technological University

Research

JoVE Journal

Engineering

10.5K 조회수.  National Institute of Standards and Technology. We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

비디오: Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel 3D/VR Interactive Environment for MD Simulations, Visualization and Analysis

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials science, biology, chemistry and physics among many others. A new computational system for the accurate and fast simulation and 3D/VR visualization of nanostructures is presented here, using the open-source molecular dynamics (MD) computer program LAMMPS. This alternative computational method uses modern graphics processors, NVIDIA CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model materials, this enhancement allows the addition of accelerated MD simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal is to investigate the structure and properties of inorganic nanostructures (e.g., silica glass nanosprings) under different conditions using this innovative computational system. The work presented outlines a description of the 3D/VR Visualization System and basic components, an overview of important considerations such as the physical environment, details on the setup and use of the novel system, a general procedure for the accelerated MD enhancement, technical information, and relevant remarks. The impact of this work is the creation of a unique computational system combining nanoscale materials simulation, visualization and interactivity in a virtual environment, which is both a research and teaching instrument at UC Merced.

A new computational system featuring GPU-accelerated molecular dynamics simulation and 3D/VR visualization, analysis and manipulation of nanostructures has been implemented, representing a novel approach to advance materials research and promote innovative investigation and alternative methods to learn about material structures with dimensions invisible to the human eye.

소설 3D / MD 시뮬레이션, 시각화 및 분석을위한 VR 대화 형 환경

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials ...

연구

공학

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

작성 및 산화물 나노 구조의 저온 특성

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

감지 및 팔라듐의 복구, 도시 광산에서 금과 코발트 금속은 나노 수레 바퀴 모양의 기공 지정 소설 센서 / 흡착제를 사용하여

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

반도체 기술과 호환 저온 탄소 나노 튜브 수직 상호 연결의 제작

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

형상 기억의 조사를 기반으로 Elastocaloric 냉각 프로세스 및 모델 검증을위한 실험 방법

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

강의의 아웃 가스 요금의 측정

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

캐스트 알루미늄 부품의 따뜻한 회전에 대한 실험 절차

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

추적 폭발물 닦아 샘플링에서 수집 효율을 측정하는 표준화 된 방법

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

에 대한 소설 방법<em&gt; 현장에서</em&gt; 나노 크기 시편의 전자 기계적 특성 분석

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Micro/Nano-scale Strain Distribution Measurement from Sampling Moir&#233; Fringes

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moir&#233; method or the spatial phase-shifting sampling moir&#233; method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moir&#233; fringes are generated to reconstruct a multiplication moir&#233; pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moir&#233; method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moir&#233; fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moir&#233; techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

A sampling moir&#233; technique featuring 2-pixel and multi-pixel sampling methods for high-accuracy strain distribution measurements at the micro/nano-scale is presented here.

샘플링 모아레 프린지에서의 마이크로 / 나노 스케일 변형률 측정

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. ...