Ringraziamo A. Sharoni da Bar-Ilan University per la fornitura dei film superconduttori. Questa ricerca è stata sostenuta dal Consiglio europeo della ricerca sovvenzione CER-2014-STG- 639792, integrazione Marie Curie Career Grant FP7-PEOPLE-2012-CIG-333.799, e Israele Science Foundation Grant ISF-1102/13.

1. L&#39;accesso a un sistema di scansione SQUID <ol><li> Utilizzare un sistema SQUID di scansione che comprende un sensore SQUID fabbricato su un chip 9, 10, stick slip fase di movimento grossolana, e uno scanner piezo-based per motion fine. Vedere la Figura 1. </li><li> Lucidare il chip SQUID in un angolo intorno al ciclo pickup. Il materiale del chip deve essere rimosso fino al prelievo del cappio. <ol><li> lucidare delicatamente il SQUID, utilizzando una carta di lucidatura 5-0,5 micron non magnetico. NOTA: Dopo la fase di lucidatura del ciclo pick-up può essere portato in prossimità, o contatto, con il campione. </li></ol></li></ol> 2. Deposizione di niobio (Nb) Thin Film con corrente continua (DC) di polverizzazione <ol><li> Ottenere un substrato. In questo lavoro, utilizzare un substrato di silicio di boro drogato con 500 nm di ossido di silicio. Altri substrati come SrTiO e MgO sono possibili. </li><li> Raggiungere una base di PRESSUre di 10 -7 Torr nella camera. Pre-sputter camera di evaporazione a temperatura ambiente con un obiettivo Nb 99,95%, in ambiente argon ad una pressione di 2,4 mTorr con una velocità di deposizione di 1,8 Å / s per 10 min. Si noti che il processo di deposizione può iniziare solo quando la pressione nella camera di base è inferiore a 10 -7 Torr. Se la pressione è più alta ripetere la fase di pre-sputtering. </li><li> Posizionare substrato nella camera. </li><li> Deposito Nb film sottile per sputtering a temperatura ambiente su un bersaglio Nb 99,95%, in ambiente argon ad una pressione di 2,4 mTorr con una velocità di deposizione di 1,8 Å / s. </li></ol> 3. Il campione-tip Allineamento <ol><li> In questa fase, allineare il sensore chip con il campione in modo che la punta del chip entra in contatto con il campione che si spostano i vortici. Per ottenere questo, utilizzare un angolo di allineamento di almeno 4 °. </li><li> Colla un cantilever flessibile su una piastra di condotta con uno strato dielettrico. Quindi, incollare il chi SQUIDp sul cantilever. La capacità tra il cantilever e una piastra statico determina il contatto con il campione e la portata della sollecitazione applicata. </li><li> campione del carico sul microscopio. Incollare il campione ad un campione designato montaggio utilizzando una pasta vernice o argento. Incollare il supporto per l&#39;elemento Z piezoelettrico (Figura 1a). </li><li> Collegare il sistema di movimento grossolano stick slip a un controller. </li><li> Impostare imaging ottico da due angolazioni - parte anteriore e il lato del chip. Utilizzare due telescopi posti su fasi di traduzione, diretto verso la parte anteriore del chip e uno dei suoi lati. </li><li> Utilizzando il stick slip fase di movimento grossolani Z, spostare il campione ad una distanza di 1 micron dal sensore, in modo che la riflessione del sensore è visibile sul campione. NOTA: Il contatto tra il campione e il sensore in questa fase possono danneggiare la SQUID. </li><li> Spostare il campione di 0,5 - 1 mm di distanza dal sensore utilizzando la fase Z stick slip movimento grossolana per evitare di danneggiare l&#39;SQUID. </li><li> Ruotare le viti di allineamento (Figura 1a) per ottenere angoli anteriori uguali (cioè, angoli ai lati della punta del chip fanno con la sua riflessione, come si vede in Figura 1c). </li><li> Spostare il campione ad una distanza di 1 micron dal sensore. Controllare gli angoli e ripetere il punto 3.7 e 3.8, se necessario. </li><li> Ruotare le viti di allineamento per ottenere un angolo di 4 gradi tra il sensore e il campione (Figura 1d). Assicurarsi che la punta del chip è la parte che entra in contatto con il campione. </li></ol> 4. Misure <ol><li> Caricare la testa di scansione (Figura 1a) ad un sistema 4 K raffreddamento. NOTA: Testina di scansione deve essere collegato a un piatto freddo, e circondato da una lattina di vuoto. Collegare una bobina attorno alla latta di applicazione di campo magnetico esterno (bassi campi di vari Gauss sono sufficienti per questo studio). Coprire questa configurazione con uno scudo Mu-metal. </li><li> Raffreddare in presenza di magnecampo tic, applicando corrente attraverso la bobina che circonda il microscopio. Scegliere accuratamente l&#39;intensità di campo per ottenere la densità desiderata vortex. Utilizzare 1Φ 0 = 20,7 G / micron 2 per calcolare il campo cooldown. Ad esempio, per 10 vortici in 10 micron dalla superficie 10 um, applicano 2.07 G. </li><li> Per il passaggio ad un nuovo campione di calore densità vortice di sopra della temperatura di transizione superconduttore (per NB, di calore superiore a 10 K). Applicare il nuovo campo. </li><li> Raffreddare campione a 4,2 K. </li><li> Girare campo magnetico fuori. Accendere SQUID su. </li><li> Spostare il campione vicino al SQUID utilizzando il sistema di movimento grossolano stick slip. <ol><li> Applicare tensioni crescenti sul cubo Z-stick slip per spostare il campione più vicino al chip SQUID. </li><li> Applicare la tensione tra la mensola e la piastra per leggere la capacità utilizzando un ponte capacità (0,1-1 V tipicamente). </li><li> Sweep la tensione sull&#39;elemento Z piezoelettrico. Misurare la capacità tra la mensola e la piattaformae. Se si verifica una grande variazione della capacità, il campione è in contatto con il chip SQUID. </li><li> Se il campione non ha fatto il contatto con il chip, ripetere i punti 4.6.1-4.6.3 fino a quando si osserva il contatto. </li><li> Opzionale: Utilizzare motion corso per regolare la distanza tra la punta e il campione in modo che il contatto avviene a basse tensioni (0 - 10 V applicata al piezo Z). </li><li> Una volta che vi sia un contatto, ripetere i punti 4.6.2-4.6.3 in diverse posizioni per determinare gli angoli di inclinazione della superficie e per definire il piano del campione, rispetto al sensore. </li></ol></li><li> Sweep la tensione sugli elementi X e Y piezoelettrici per spostare il campione rispetto al sensore. Scansione ad un&#39;altezza costante sopra il campione, senza contatto tra la punta e il campione, per mappare la distribuzione vortice. Ottenere una altezza scansione costante variando la tensione sul piezo Z secondo le posizioni X e Y, e al piano definito in 4.6. </li><li> Scegli un vortice e scansione arouND di determinare con precisione la posizione del suo centro. Si noti che la posizione vortice è relativo al prelievo del cappio del SQUID, non al punto di contatto. </li><li> Girare SQUID off. </li><li> Applicare una tensione che è superiore alla tensione touchdown alla z piezo eo rubinetto vicino al centro del vortice o spazzare il vortice trascinando il sensore (a contatto con il campione) lentamente il campione ad una posizione desiderata. Il vortice si muoverà verso il rubinetto o in senso ampio. Valori tipici per aggiungere alla tensione piezo z applicata sono 2-5 V. </li><li> Accendere SQUID su. </li><li> Immagine nuovamente ad un&#39;altezza costante senza contatto per individuare la nuova posizione del vortice. </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.

manipolazione di successo di vortici dipende da diversi passaggi critici. È importante allineare il sensore ad un angolo, in modo che la punta del chip sarà il primo a fare contatto con il campione. In secondo luogo, è importante notare che la forza esercitata sul campione è determinata dalle proprietà meccaniche del cantilever che il chip è montato. Nel regime elastica, la forza applicata è proporzionale alla deflessione, x, secondo la legge di Hooke: F = -kx Se k è la costan...

Vortici sono oggetti magnetici su scala nanometrica, costituite tipo 2 superconduttori in presenza di campo magnetico esterno. In un campione privo di difetti, vortici possono muoversi liberamente. Tuttavia, diversi difetti nel risultato materiale in regioni di superconduttività ridotta che sono energeticamente favorevole per vortici. Vortici tendono a decorare queste regioni, noti anche come i siti di pinning. In questo caso, la forza necessaria per spostare un vortice deve essere maggiore della forza pinning. Proprietà di vortici, come la densità vortice, forza di interazione e gamma, possono essere facilmente determinati dal campo esterno, la temperatura o la geometria del campione. La capacità di controllare queste proprietà loro un buon sistema modello per il comportamento materia condensata che può essere facilmente regolato, nonché idonei per applicazioni elettroniche 1, 2 rende. Il controllo della posizione dei singoli vortici è essenziale per la progettazione di tale loElementi gici. Controllo meccanico delle nanoparticelle magnetiche era stato raggiunto prima. Kalisky et al. recentemente utilizzato scansione superconduttori dispositivo interferenza quantistica (SQUID) per studiare l&#39;influenza di stress meccanico locale sulla patch ferromagnetici nelle interfacce di ossidi complessi 3. Sono stati in grado di cambiare l&#39;orientamento del patch di scansione a contatto, premendo la punta del SQUID nel campione, applicando una forza di fino a 1 μN nel processo. Abbiamo usato un metodo simile nel nostro protocollo per spostare vortici. In studi esistenti di manipolazione vortice, movimento è stata ottenuta applicando corrente al campione, creando così Lorentz forza 4, 5, 6. Mentre questo metodo è efficace, non è locale, e per controllare un singolo vortice, è necessaria fabbricazione aggiuntivo. Vortici possono anche essere manipulated applicando campo magnetico esterno, per esempio con un microscopio a forza magnetica (MFM) o con una bobina di campo SQUID 7, 8. Questo metodo è efficace e locale, ma la forza applicata da questi strumenti è piccola, e può superare la forza pinning solo ad alte temperature, vicino alla temperatura critica del superconduttore. Il nostro protocollo permette efficace, manipolazione locale a basse temperature (4 K) senza ulteriore realizzazione del campione. Abbiamo vortici di immagini usando la microscopia a scansione SQUID. Il sensore è fabbricato in un chip di silicio che è lucidato in un angolo, e incollato su un cantilever flessibile. Il cantilever viene utilizzato per il rilevamento capacitivo della superficie. Il chip è posto ad un angolo al campione, in modo che il punto di contatto è sulla punta del chip. Applichiamo forze fino a 2 μN spingendo il chip nel campione. Si passa il campione relativo al SQUID da elementi piezoelettrici. Ci muoviamoil vortice toccando la punta di silicio accanto ad un vortice, o da spazzare esso, toccando il vortice.

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			<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>
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		<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.

Il nostro protocollo è stato testato con successo su migliaia di singoli, vortici ben separati in due campioni di Nb, e nove campioni di NbN. Noi generiamo nuovi vortici sullo stesso campione riscaldando il campione sopra Tc, e raffreddamento di nuovo a 4,2 K in presenza di un campo magnetico. Abbiamo scelto il campo magnetico esterno per ottenere la densità desiderata vortex. Mostriamo qui i dati da questi esperimenti. Questi risultati sono stati descritti in dettaglio da Kremen e...

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.

La scansione SQUID Studio di Vortex manipolazione da locale Contatto

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

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JoVE Journal

Engineering

6.8K Views.  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. 

Video: 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.

Scansione-sonda a singolo elettrone Capacità Spettroscopia

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

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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.

Analisi di contatto Interfacce semplici dispositivi GaN nanowire

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.

Monostrato Contatto doping di silicio superfici e nanofili Uso organofosforici Composti

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.

In analisi di profondità di LED da una combinazione di raggi X Tomografia Computerizzata (TC) e microscopia ottica (LM) correlata con microscopia elettronica a scansione (SEM)

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.

Caratterizzazione completa dei difetti estesi in materiali semiconduttori da un microscopio elettronico a scansione

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.

A mano controllata manipolazione di singole molecole attraverso un microscopio a scansione di sonda con una realtà virtuale 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.

L&#39;utilizzo di nanoparticelle sacrificali per eliminare gli effetti del colpo-rumore in fori di contatto fabbricato da E-litografia a fascio

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.

Precisione fresatura di Nanotubi di carbonio delle foreste Utilizzando bassa pressione 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.

Misure del carbonio nel suolo di neutroni-Gamma analisi statica e modalità di scansione

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.

Fabbricazione di nanostrutture magnetiche sulle membrane di nitruro di silicio per studi di vortice magnetico utilizzando tecniche di microscopia di trasmissione

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