Name: fabrication of 109&#176; periodic domain walls with a bottom electrode in bifeo3 thin films
Uploaded: 2017-05-08T12:02:39
Description: A variety of exciting phenomena have been discovered using 109&#176; domain walls in BiFeO3 thin films, such as domain wall conductivity, photovoltaic ...

The work was supported by the National Key Research and Development Program of China (No. 2016YFA0201002) and NSFC (Grant Nos. 51431006, 11474146, 61674062, and 51602110).

1. Substrate Preparation
<ol>
	<li>Clean a 5 mm &#215; 5 mm &#215; 0.5 mm single-crystal DyScO3 (110) substrate with acetone in an ultrasonic cleaner for 5 min.</li>
	<li>Rinse the substrate with acetone for 5 s and transfer it to isopropyl alcohol. Clean it for 5 min in the ultrasonic cleaner.</li>
	<li>Rinse the substrate with isopropyl alcohol for 5 s and dry it using N2 flow.</li>
	<li>Mount the substrate on a heater with silver paint and then put the heater on a hot plate to dry the silver pa...

<ol>
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PLD is a powerful technique to fabricate complex oxide epitaxial thin films19. Using this technique, many investigations have been carried out on BiFeO3 thin films13,20,21,22. As one of the most striking aspects, domain walls are widely studied due to a wealth of fascinating phenomena1,2,<su...

Domain wall functionalities in BiFeO3 thin films, such as domain wall conductivity1, photovoltaic effects2, magnetism3, and magnetoelectric coupling4, have inspired many studies on the fabrication and manipulation of the domain structures5,6,7. Periodically ordered 71&#176;, 109&#176;, and 180&#176; stripe domains have been obtained by tuning the film thickness effects, misfit strain effects, and electrostatic boundary conditions8,9,10,11. The periodic 71&#176; stripe domain structure can be produced on thick SrRuO3 bottom electrodes and can be reversibly controlled under an electric field8, which has promoted a series of seminal works on the electric-field control of magnetism in the ferromagnet/multiferroic BiFeO3 system4,12,13,14,15. However, the pure 109&#176; stripe domain structure can only exist without a (or with an ultra-thin) SrRuO3 bottom electrode8, making it typically unstable or unresponsive under an applied electric field and inhibiting the study of the switching behavior of 109&#176; domains. Moreover, a large exchange bias has been demonstrated in the ferromagnet/BiFeO3 system with the 109&#176; BiFeO3 domain walls16,17. Thus, the successful fabrication of a 109&#176; domain structure with a bottom electrode is promising for controlling exchange bias using an electric field. This has great potential application to low-energy-consumption, non-volatile magnetoelectronic memory devices.
Our previous study18 revealed a novel approach to precisely control the domain structure in BiFeO3 thin films by tuning the depolarization field with a dielectric layer. In the BiFeO3/SrRuO3/DyScO3 stack without La-BiFeO3, the screening effects at the ferroelectric (BiFeO3)/metallic (SrRuO3) interface enable the formation of 71&#176; domains, while the introduction of the La-BiFeO3 dielectric space layer enables an increase in the distance between the screening charges from the SrRuO3 and BiFeO3. This leads to a reduction of the screening effects and thus an increase in the depolarization field. Consequently, the 71&#176; stripe domain is destabilized and a 109&#176; stripe domain structure forms to decrease the energy cost due to the strong depolarization field.
In this work, we focus on the fabrication of 109&#176; periodic domain walls with a bottom electrode in BiFeO3 thin films by introducing a La-BiFeO3 dielectric layer. The detailed protocol describes how to grow the multilayer thin films using PLD and how to use piezoresponse force microscopy (PFM) to measure the 109&#176; domain structure and study its switching behavior. The typical PLD system is shown in Figure 1. This protocol can help to increase the reproducibility of the fabrication of 109&#176; periodic domain walls and promote the study of domain wall functionality.

<table>
	<tbody>
		<tr>
			<td>Pulsed Laser</td>
			<td>Coherent</td>
			<td>Complex Pro 205 F</td>
			<td></td>
		</tr>
		<tr>
			<td>Power Meter</td>
			<td>Coherent</td>
			<td>FieldMaxII</td>
			<td></td>
		</tr>
		<tr>
			<td>Target</td>
			<td>Home Made</td>
			<td>Made on request</td>
			<td></td>
		</tr>
		<tr>
			<td>Piezoresponse Force Microscopy</td>
			<td>Oxford Insturments</td>
			<td>MFP-3D Infinity Asylum Research AFM</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl Alcohol</td>
			<td>Fisher Chemical</td>
			<td>A415-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Actone</td>
			<td>Fisher Chemical</td>
			<td>A949-4</td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication of 109&#176; periodic domain walls with a bottom electrode in bifeo3 thin films

A variety of exciting phenomena have been discovered using 109&#176; domain walls in BiFeO3 thin films, such as domain wall conductivity, photovoltaic effects, and magnetoelectric coupling effects. The control of these physical properties with an electric field plays a key role in the development of nanoelectric devices. Therefore, it is critical to fabricate 109&#176; periodic domain walls with a bottom electrode. However, the introduction of a bottom electrode favors the formation of a 71&#176; domain structure due to the electrostatic boundary conditions. In this study, pulsed laser deposition (PLD) is used to produce multilayer epitaxial thin films. A 25% La doping BiFeO3 layer is inserted as the dielectric spacer between the bottom electrode SrRuO3 layer and the pure BiFeO3 layer, enabling the fabrication of 109&#176; periodic domain walls engineered by an interface effect-depolarization field. Moreover, the fabrication of the 109&#176; domain structure with a bottom electrode enables the study of its switching behavior. This protocol provides a novel route to produce 109&#176; periodic domain walls and opens a new pathway to explore fascinating phenomena, such as the room-temperature electric field control of exchange bias in a ferromagnet/BiFeO3 system and room-temperature multiferroic vortices in BiFeO3.

The multilayer BiFeO3/La-BiFeO3/SrRuO3films on the DyScO3 (110) substrate are produced by PLD, and the heterostructure stack is shown in Figure 2. To obtain the 109&#176; domain structure with a bottom electrode, a thin dielectric layer of La-BiFeO3 is inserted between the SrRuO3 bottom electrode and the ferroelectric BiFeO3 layer.
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109&#176; periodic domain walls can successfully be fabricated by introducing a dielectric La-BiFeO3 layer between a bottom electrode and a ferroelectric BiFeO3 layer, enabling the study of the switching behavior of a 109&#176; domain structure and the investigation of the electric field control of exchange bias in a ferromagnet/BiFeO3 system.

Fabrication of 109&#176; Periodic Domain Walls with a Bottom Electrode in BiFeO3 Thin Films

A variety of exciting phenomena have been discovered using 109&#176; domain walls in BiFeO3 thin films, such as domain wall conductivity, photovoltaic ...