Agradecemos a A. Sharoni da Universidade de Bar-Ilan para a prestação dos filmes supercondutores. Esta pesquisa foi apoiada pelo Conselho Europeu de Investigação Grant ERC-2014-STG- 639.792, Integração Marie Curie Career Grant FP7-PEOPLE-2012-CIG-333799, e Israel Science Foundation Grant ISF-1102/13.

1. O acesso a um Sistema de Digitalização SQUID <ol><li> Use um sistema de SQUID de digitalização que inclui um sensor SQUID fabricado num chip de 9, 10, vara deslizamento estágio movimento grosseiro, e um scanner baseado em piezo para o movimento bem. Veja a Figura 1. </li><li> Polir o chip SQUID em um canto em torno do laço de recolhimento. O material do chip tem de ser removido todo o caminho para o circuito de captação. <ol><li> Gentilmente polir o SQUID, usando um 5-0,5 mm de papel de polimento não magnético. NOTA: Após a fase de polimento do circuito de captação pode ser posta em proximidade ou contato, com a amostra. </li></ol></li></ol> 2. Deposição de nióbio (Nb) Thin Film com Corrente contínua (CC) Sputtering <ol><li> Obter um substrato. Neste trabalho, utilizar um substrato de silício dopado com boro, com 500 nm de óxido de silício. Outros substratos tais como SrTiO e MgO são possíveis. </li><li> Chegar a um pressu de basere de 10 -7 Torr na câmara. Pré-sputter da câmara de evaporação à temperatura ambiente com um alvo Nb 99,95%, em ambiente de árgon, a uma pressão de 2,4 mTorr com uma velocidade de deposição de 1,8 Ã / s para 10 min. Note-se que o processo de deposição pode começar apenas quando a pressão de base da câmara é inferior a 10 -7 Torr. Se a pressão é maior repita a fase de pré-pulverização catódica. </li><li> Coloque substrato na câmara. </li><li> Depósito Nb película fina por pulverização catódica à temperatura ambiente a partir de um alvo Nb 99,95%, em ambiente de árgon, à pressão de 2,4 mTorr com uma velocidade de deposição de 1,8 Ã / s. </li></ol> Alinhamento 3. Sample-tip <ol><li> Nesta etapa, o chip sensor alinhar com a amostra de forma que a ponta do chip faz contacto com a amostra quando se deslocam os vórtices. Para conseguir isso, usar um ângulo de alinhamento de pelo menos 4 ° C. </li><li> Cole um braço de suporte flexível em uma placa condutora com uma camada de dieléctrico. Em seguida, cole o chi SQUIDp sobre o cantilever. A capacitância entre o cantilever e uma placa estática determina o contato com a amostra e a extensão da tensão aplicada. </li><li> amostra de carga sobre o microscópio. Cole a amostra a uma amostra designada montagem usando um verniz ou prata colar. Cole a montagem ao elemento Z piezo (Figura 1a). </li><li> Ligue o sistema de movimento grossa vara de deslizamento para um controlador. </li><li> Configurar imageamento óptico de dois ângulos - a frente eo lado do chip. Usar dois telescópios colocados em estágios de translação, dirigido para a frente de o chip e um dos seus lados. </li><li> Utilizando a vara Z deslizamento fase grosseira movimento, mover-se a amostra a uma distância de 1 uM a partir do sensor, de modo que a reflexão do sensor é visível na amostra. NOTA: Entre em contato entre a amostra e o sensor nesta fase pode prejudicar o SQUID. </li><li> Mova a amostra de 0,5 - 1 mm de distância do sensor utilizando a fase Z vara deslizamento movimento grossa para evitar danos ao SLIBRA. </li><li> Girar a parafusos de alinhamento (Figura 1a) para obter ângulos frontais iguais (ou seja, os ângulos dos lados da ponta do chip fazer com sua reflexão, como pode ser visto na Figura 1c). </li><li> Mover a amostra a uma distância de 1 uM a partir do sensor. Verifique os ângulos e repita o passo 3.7 e 3.8, se necessário. </li><li> Rodar os parafusos de alinhamento para obter um ângulo de 4 graus entre o sensor e a amostra (Figura 1D). Certifique-se a ponta do chip é a parte que entra em contato com a amostra. </li></ol> 4. medições <ol><li> Coloque a cabeça de digitalização (Figura 1a) para um sistema de 4 K de resfriamento. NOTA: cabeça de digitalização deve ser conectado a uma placa fria, e rodeado por uma lata de vácuo. Ligar uma bobina em torno da lata para aplicação de um campo magnético externo (baixos campos de vários Gauss são suficientes para este estudo). Cubra essa configuração com um escudo Mu-metal. </li><li> Legal, na presença de magneTic campo, através da aplicação de corrente através da bobina em torno do microscópio. Escolha a intensidade do campo cuidadosamente para conseguir a densidade desejada vórtice. Use 1Φ = 0 20,7 g / uM 2 para calcular o campo de recarga. Por exemplo, para 10 vórtices em um 10 um por 10 uM área, aplicam-se 2,07 G. </li><li> Para alterar para a nova amostra de calor densidade vórtice acima da temperatura de transição supercondutora (Para Nb, aqueça acima de 10 K). Aplicar o novo campo. </li><li> amostra legal para 4,2 K. </li><li> Vire campo magnético fora. Vire SQUID diante. </li><li> Mova a amostra perto do SQUID usando o sistema de movimento grossa vara de deslizamento. <ol><li> Aplique tensões crescentes no cubo Z-stick deslizamento para mover a amostra mais próxima do chip SQUID. </li><li> Aplicar a tensão entre o braço de suporte e a placa de leitura a capacitância usando uma ponte de capacitância (0,1-1 V tipicamente). </li><li> Varrer a tensão no elemento piezo Z. Medir a capacitância entre o cantilever ea plate. Se uma grande alteração na capacitância ocorre, a amostra está em contacto com o chip SQUID. </li><li> Se a amostra não fazer contato com o chip, repita os passos 4.6.1-4.6.3 até que o contato é observado. </li><li> Opcional: Use curso de movimento para ajustar o espaçamento entre a ponta e a amostra de modo que o contacto ocorre a baixas tensões (0 - 10 V aplicada na Z piezo). </li><li> Uma vez que não há contacto, repetir os passos 4.6.2-4.6.3 em vários locais, a fim de determinar os ângulos de inclinação da superfície e para definir o plano da amostra, em relação ao sensor. </li></ol></li><li> Varrer a tensão nos elementos piezoeléctricos X e Y de modo a mover-se a amostra em relação ao sensor. Digitalizar a uma altura constante acima da amostra, sem contacto entre a ponta e a amostra, a fim de mapear a distribuição de vórtice. Atingir uma altura constante de digitalização, alterando a tensão sobre o piezo Z de acordo com os locais X e Y, e ao plano definido em 4.6. </li><li> Escolha um vórtice e digitalizar around-lo para determinar com precisão a localização do seu centro. Note-se que a localização vortex é relativo ao ciclo de captação da lula, não ao ponto de contacto. </li><li> Vire SQUID off. </li><li> Aplicar uma tensão que é maior do que a tensão de aterragem ao piezo e ou z torneira ao lado do centro do vórtice ou varrer o vórtice, arrastando o sensor (em contacto com a amostra) lentamente sobre a amostra a um local desejado. O vórtice vai avançar para a torneira ou na direção de varredura. Os valores típicos para adicionar à tensão piezoeléctrica aplicada z são 2-5 V. </li><li> Vire SQUID diante. </li><li> Imagem novamente a uma altura constante, sem contacto para localizar a nova localização do vórtice. </li></ol>

<ol>
	<li>Olson Reichhardt, C. J., Hastings, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+Vortices+Entangle?.">Do Vortices Entangle?.</a> Phys. Rev. Lett. 92, 157002 (2004).</li><li>Milo&#353;evi&#263;, M. V., Berdiyorov, G. R., Peeters, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluxonic+cellular+automata.">Fluxonic cellular automata.</a> Appl. Phys. Lett. 91, 212501 (2007).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scanning+Probe+Manipulation+of+Magnetism+at+the+LaAlO3/SrTiO3+Heterointerface.">Scanning Probe Manipulation of Magnetism at the LaAlO3/SrTiO3 Heterointerface.</a> Nano Lett. 12, 4055-4059 (2012).</li><li>Silva, C. C. D. S., Van de Vondel, J., Morelle, M., Moshchalkov, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+multiple+reversals+of+a+ratchet+effect.">Controlled multiple reversals of a ratchet effect.</a> Nature. 440, 651-654 (2006).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+single+vortices+in+grain+boundaries:+I-V+characteristics+on+the+femtovolt+scale.">Dynamics of single vortices in grain boundaries: I-V characteristics on the femtovolt scale.</a> Appl. Phys. Lett. 94, 202504 (2009).</li><li>Embon, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+dynamics+and+pinning+of+single+vortices+in+superconductors+at+nanometer+scales.">Probing dynamics and pinning of single vortices in superconductors at nanometer scales.</a> Sci. Rep. 5, 7598 (2015).</li><li>Auslaender, O. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanics+of+individual+isolated+vortices+in+a+cuprate+superconductor.">Mechanics of individual isolated vortices in a cuprate superconductor.</a> Nature Phys. 5, 35-39 (2008).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavior+of+vortices+near+twin+boundaries+in+underdoped+Ba(Fe1-xCox)2As2.">Behavior of vortices near twin boundaries in underdoped Ba(Fe1-xCox)2As2.</a> Phys. Rev. B. 83, 064511 (2011).</li><li>Huber, M. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gradiometric+micro-SQUID+susceptometer+for+scanning+measurements+of+mesoscopic+samples.">Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples.</a> Rev. Sci. Instrum. 79, 053704 (2008).</li><li>Koshnick, N. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+terraced+scanning+super+conducting+quantum+interference+device+susceptometer+with+submicron+pickup+loops.">A terraced scanning super conducting quantum interference device susceptometer with submicron pickup loops.</a> Appl. Phys. Lett. 93, 243101 (2008).</li><li>Kremen, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+Control+of+Individual+Superconducting+Vortices.">Mechanical Control of Individual Superconducting Vortices.</a> Nano Lett. 16, 1626-1630 (2016).</li></ol>

The authors have nothing to disclose.

manipulação bem sucedida de vórtices depende de vários passos críticos. É importante para alinhar o sensor a um ângulo, de tal modo que a ponta do chip será o primeiro a fazer o contacto com a amostra. Em segundo lugar, é importante notar que a força exercida sobre a amostra é determinada pelas propriedades mecânicas do cantilever que o chip é montado. No regime elástica, a força exercida é proporcional à deflexão, X, de acordo com a lei de Hooke: F = -kx Onde k é a...

Vórtices são objetos magnéticos em nanoescala, formada em tipo 2 supercondutores na presença de um campo magnético externo. Em uma amostra livre de defeitos, vórtices podem se mover livremente. No entanto, diferentes defeitos no resultado de material nas regiões da supercondutividade reduzida que são energeticamente favorável para vórtices. Vórtices tendem a decorar estas regiões, também conhecidos como os locais de fixação. Neste caso, a força necessária para mover um vórtice deve ser maior do que a força de fixação. Propriedades de vórtices, tais como a densidade de vórtice, a força interacção e gama, pode ser facilmente determinada por um campo externo, a temperatura, ou a geometria da amostra. A capacidade de controlar estas propriedades que os torna um bom sistema modelo para o comportamento da matéria condensada que pode ser facilmente afinado, bem como candidatos adequados para aplicações electrónicas 1, 2. O controlo da localização dos vórtices individuais é essencial para a concepção de tais Loelementos gicos. controle mecânico de nanopartículas magnéticas tinha sido alcançado antes. Kalisky et ai. recentemente utilizado digitalização supercondutores quantum interference device (SQUID) para estudar a influência do estresse mecânico local no manchas ferromagnéticos nas interfaces de óxido complexo 3. Eles foram capazes de alterar a orientação do penso por varrimento em contacto, pressionar a ponta da lula na amostra, aplicando uma força de 1 até μN no processo. Temos utilizado um método semelhante em nosso protocolo, a fim de mover vórtices. Em estudos existentes sobre a manipulação do vortex, movimento foi conseguido através da aplicação de corrente com a amostra, assim criando força de Lorentz 4, 5, 6. Enquanto este método é eficaz, não é local, e, a fim de controlar uma única vórtice, fabricação adicional é necessária. Vórtices também pode ser manippovoadas por aplicação de um campo magnético externo, por exemplo com um microscópio de força magnética (MFM) ou com uma bobina de campo SQUID 7, 8. Este método é eficaz e local, mas a força exercida por estas ferramentas é pequena, e pode superar a força fixando-se apenas com altas temperaturas, próximas da temperatura crítica do supercondutor. Nosso protocolo permite uma manipulação eficaz, local, a baixas temperaturas (4 K) sem fabricação adicional da amostra. Nós imagem vórtices usando microscopia de varredura SQUID. O sensor é fabricado num chip de silício, que é polida para um canto, e colado sobre um braço de suporte flexível. O braço de suporte é utilizado para detecção capacitiva da superfície. O chip é colocado em ângulo com a amostra, de modo que o ponto de contacto está na ponta do chip. Nós aplicar forças de até 2 μN empurrando o chip na amostra. Movemo-nos a amostra em relação ao SQUID por elementos piezo. Nós movemoso vórtice tocando a ponta de silício ao lado de um vórtice, ou por varrendo-o, tocar o vórtice.

<table border="0" cellpadding="0" cellspacing="0" width="837">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">stick slip coarse motion system</td>
			<td style="width:207px;">attocube</td>
			<td style="width:135px;">ANPx-101</td>
			<td style="width:199px;">x,y motion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">stick slip coarse motion system</td>
			<td style="width:207px;">attocube</td>
			<td style="width:135px;">ANPz-101</td>
			<td>z motion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">stick slip coarse motion system controller</td>
			<td style="width:207px;">Attocube</td>
			<td style="width:135px;">ANC 300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">high voltage amplifier</td>
			<td style="width:207px;">Attocube</td>
			<td style="width:135px;">ANC 250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">data acquisition card</td>
			<td style="width:207px;">National Instruments</td>
			<td style="width:135px;">NI&#160;PCIe-6363</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">piezo elements</td>
			<td style="width:207px;">Piezo Systems Inc</td>
			<td style="width:135px;">T2C</td>
			<td>non magnetic</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">low noise voltage preamplifier</td>
			<td style="width:207px;">Stanford Research Systems</td>
			<td style="width:135px;">SR 560</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">capacitance bridge</td>
			<td style="width:207px;">General Radio</td>
			<td style="width:135px;">1615A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">telescope</td>
			<td style="width:207px;">NAVITAR</td>
			<td style="width:135px;">1-504516</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">camera</td>
			<td style="width:207px;">MOTICAM</td>
			<td style="width:135px;">MP2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">dewar</td>
			<td style="width:207px;">Cryofab</td>
			<td style="width:135px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">insert</td>
			<td style="width:207px;">ICE oxford</td>
			<td style="width:135px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Mu-metal shield</td>
			<td style="width:207px;">Amuneal</td>
			<td style="width:135px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">vacuum cap</td>
			<td style="width:207px;">ICE oxford</td>
			<td style="width:135px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">sputtering system</td>
			<td style="width:207px;">AJA international Inc</td>
			<td style="width:135px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">lapping film</td>
			<td style="width:207px;">3M</td>
			<td style="width:135px;">261X</td>
			<td>non magnetic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Nb target</td>
			<td style="width:207px;">Kurt J. Lesker</td>
			<td style="width:135px;">EJTNBXX351A2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">GE Varnish</td>
			<td style="width:207px;">CMR-Direct</td>
			<td style="width:135px;">02-33-001</td>
			<td>for cryogenic heatsinking</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:299px;">Silver paste</td>
			<td style="width:207px;">Structure Probe Inc</td>
			<td style="width:135px;">05063-AB</td>
			<td></td>
		</tr>
	</tbody>
</table>

scanning squid study of vortex manipulation by local contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

O protocolo foi testado com sucesso em milhares de vórtices individuais, bem separadas em duas amostras de Nb, e nove amostras de NBN. Geramos novos vórtices sobre a mesma amostra por aquecimento da amostra acima de Tc, e arrefecendo-o de volta para 4,2 K na presença de um campo magnético. Nós escolhemos o campo magnético externo para atingir a densidade desejada vórtice. Mostramos aqui dados a partir destas experiências. Estes resultados foram descritos em detalhe por Kremen <em...

Watch this Scientific Journal Video about Scanning SQUID Study of Vortex Manipulation by Local Contact at JoVE.com

Scanning SQUID Study of Vortex Manipulation by Local Contact

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

Digitalizar Estudo SQUID de Manipulação Vortex por contato local

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

scanning-squid-study-of-vortex-manipulation-by-local-contact

Research

JoVE Journal

Engineering

6.8K visualizações.  Bar-Ilan University. We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps. 

Vídeo: Scanning SQUID Study of Vortex Manipulation by Local Contact

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

-Sonda de varredura único elétron Espectroscopia de capacitância

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Engenharia

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

Análise de Contato Interfaces para únicos dispositivos de nanofios de GaN

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

In Depth Analyses of LEDs by a Combination of X-ray Computed Tomography (CT) and Light Microscopy (LM) Correlated with Scanning Electron Microscopy (SEM)

In failure analysis, device characterization and reverse engineering of light emitting diodes (LEDs), and similar electronic components of micro-characterization, plays an important role. Commonly, different techniques like X-ray computed tomography (CT), light microscopy (LM) and scanning electron microscopy (SEM) are used separately. Similarly, the results have to be treated for each technique independently. Here a comprehensive study is shown which demonstrates the potentials leveraged by linking CT, LM and SEM. In depth characterization is performed on a white emitting LED, which can be operated throughout all characterization steps. Major advantages are: planned preparation of defined cross sections, correlation of optical properties to structural and compositional information, as well as reliable identification of different functional regions. This results from the breadth of information available from identical regions of interest (ROIs): polarization contrast, bright and dark-field LM images, as well as optical images of the LED cross section in operation. This is supplemented by SEM imaging techniques and micro-analysis using energy dispersive X-ray spectroscopy.

In Depth Analyses of LEDs by a Combination of X-ray Computed Tomography CT and Light Microscopy LM Correlated with Scanning Electron Microscopy SEM

A workflow for comprehensive micro-characterization of active optical devices is outlined. It contains structural as well as functional investigations by means of CT, LM and SEM. The method is demonstrated for a white LED which can be still be operated during characterization.

Em análises profundidade de LEDs por uma combinação de raios-X Tomografia Computadorizada (CT) e Microscopia de Luz (LM) correlacionada com Microscopia Eletrônica de Varredura (MEV)

In failure analysis, device characterization and reverse engineering of light emitting diodes (LEDs), and similar electronic components of ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

Caracterização abrangente de Defeitos estendidos em Materiais Semicondutores por um Microscópio Eletrônico de Varredura

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits &#34;hand controlled manipulation&#34; (HCM), in which the SPM tip is moved according to the motion of the experimenter&#39;s hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

We demonstrate the precise manipulation of individual organic molecules on a metal surface with the tip of a scanning probe microscope driven in 3D by the experimenter's hand using a motion capture system and fully immersive virtual reality goggles.

Mão Controlado Manipulação de solteiro moléculas através de um Scanning Probe Microscope com uma interface de realidade virtual 3D

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building ...

Use of Sacrificial Nanoparticles to Remove the Effects of Shot-noise in Contact Holes Fabricated by E-beam Lithography

Nano-patterns fabricated with extreme ultraviolet (EUV) or electron-beam (E-beam) lithography exhibit unexpected variations in size. This variation has been attributed to statistical fluctuations in the number of photons/electrons arriving at a given nano-region arising from shot-noise (SN). The SN varies inversely to the square root of a number of photons/electrons. For a fixed dosage, the SN is larger in EUV and E-beam lithographies than for traditional (193 nm) optical lithography. Bottom-up and top-down patterning approaches are combined to minimize the effects of shot noise in nano-hole patterning. Specifically, an amino-silane surfactant self-assembles on a silicon wafer that is subsequently spin-coated with a 100 nm film of a PMMA-based E-beam photoresist. Exposure to the E-beam and the subsequent development uncover the underlying surfactant film at the bottoms of the holes. Dipping the wafer in a suspension of negatively charged, citrate-capped, 20 nm gold nanoparticles (GNP) deposits one particle per hole. The exposed positively charged surfactant film in the hole electrostatically funnels the negatively charged nanoparticle to the center of an exposed hole, which permanently fixes the positional registry. Next, by heating near the glass transition temperature of the photoresist polymer, the photoresist film reflows and engulfs the nanoparticles. This process erases the holes affected by SN but leaves the deposited GNPs locked in place by strong electrostatic binding. Treatment with oxygen plasma exposes the GNPs by etching a thin layer of the photoresist. Wet-etching the exposed GNPs with a solution of I2/KI yields uniform holes located at the center of indentations patterned by E-beam lithography. The experiments presented show that the approach reduces the variation in the size of the holes caused by SN from 35% to below 10%. The method extends the patterning limits of transistor contact holes to below 20 nm.

Uniformly sized nanoparticles can remove fluctuations in contact hole dimensions patterned in poly(methyl methacrylate) (PMMA) photoresist films by electron beam (E-beam) lithography. The process involves electrostatic funneling to center and deposit nanoparticles in contact holes, followed by photoresist reflow and plasma- and wet-etching steps.

Uso de sacrificiais nanopartículas para eliminar os efeitos do Plano de ruído em contato Buracos fabricada por E-beam litografia

Nano-patterns fabricated with extreme ultraviolet (EUV) or electron-beam (E-beam) lithography exhibit unexpected variations in size. This variation has ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

Precision Fresagem de Nanotubos de Carbono Florestas Usando Baixa Pressão Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

Medições de carbono no solo por nêutrons-Gamma análise estática e modos de digitalização

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

Fabricação de nanoestruturas magnéticas nas membranas de nitreto de silício para estudos de vórtice magnético utilizando técnicas de microscopia de transmissão

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared ...