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Domain wall motion in stoichiometric LiTaO3 induced by low-energy electron beam
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.ORCID-id: 0000-0003-2070-9167
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.ORCID-id: 0000-0001-7688-1367
2019 (Engelska)Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Artikel i tidskrift, Letter (Refereegranskat) Submitted
Abstract [en]

Scanning electron microscopy was used to study the mobility of domain walls in vapor-transport equilibrated stoichiometric LiTaO3. By using low-acceleration voltage, switching occurs solely for polarization pointing-up domains, resulting in fast domain-wall motion. When the incoming electron beam was more energetic with larger penetration depth, the switching instead occurred for polarization pointing down domains. Our results are discussed in terms of the interaction of the scanning electron beam with the polarization-screening charges at the crystal surface.

Ort, förlag, år, upplaga, sidor
2019.
Nyckelord [en]
ferroelectrics, domain wall
Nationell ämneskategori
Annan fysik
Identifikatorer
URN: urn:nbn:se:kth:diva-249385OAI: oai:DiVA.org:kth-249385DiVA, id: diva2:1304265
Anmärkning

QC 20190412

Tillgänglig från: 2019-04-11 Skapad: 2019-04-11 Senast uppdaterad: 2019-04-12Bibliografiskt granskad
Ingår i avhandling
1. Studies on Domain Dynamics in Nonlinear Optical Ferroelectric Oxide Crystals
Öppna denna publikation i ny flik eller fönster >>Studies on Domain Dynamics in Nonlinear Optical Ferroelectric Oxide Crystals
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Nonlinear optical frequency conversion is the key technology for modifying laser output radiation, in order to target specific applications. The most powerful technique to obtain tailored second-order nonlinear interactions is the quasi-phasematching (QPM) approach. QPM is based on periodic modulation of the medium’s nonlinearity and allows versatile and efficient frequency conversion in the whole transparency region of the material. QPM is commonly implemented in ferroelectric oxide crystals by periodically inverting the spontaneous polarization, so-called, periodic poling. However, in order to achieve QPM structures of practical relevance, both the optical properties of the material and the domain engineering techniques have to be suitable for the targeted nonlinear interaction.

Rb-doped KTiOPO4 (RKTP) and vapor-transport-equilibrated stoichiometric LiTaO3 (VTE-SLT) are two of the most promising ferroelectric oxides used for nonlinear optics. The former is suitable for high peak-power applications and for engineering of QPM devices with sub-µm periodicity. The latter shows a short cut-off wavelength with low linear absorption, which makes it very attractive for UV-light generation. However, in order to fully exploit the potential of these two materials, it is of utmost importance to understand the domain dynamics and stability from a fundamental point of view, as well as to investigate ways to overcome their limitations.

This thesis presents studies on domain dynamics and stability in these two materials. A novel method for periodic poling of RKTP has been investigated. The method, based on using a micro-structured silicon chip as the contact electrode, has been used to fabricate periodically poled RKTP crystals with 9.01 µm period. The samples became well-poled and showed high conversion efficiency for second harmonic generation. The domain dynamics, when the silicon stamp was used as an electrode were studied, showing potential for short-pitch poling and complex patterning.

Furthermore, the domain stability in RKTP during thermal annealing at high temperatures was investigated. The results show anisotropic domain wall motion, with severe domain contraction along the crystallographic b-axis when the periodicity was reduced. A technique to suppress this domain contraction was developed based on dicing away the edges of the QPM grating so that the domain b-faces terminate in air. This gave excellent results for a broad range of periodicities.

Studies of the domain stability of periodically poled VTE-SLT during chemical etching were performed by on-line second harmonic generation, and optical microscopy. The results show that wet etching directly after poling leads to domain-wall motion, resulting in back-switching or domain merging. 

Furthermore, the domain wall motion induced by electron beam irradiation was investigated using a scanning electron microscope. It was found that domain switching strongly depends on the ratio of secondary electrons to incident electrons. These results are discussed in terms of electron beam and screening charges interaction.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2019. s. 79
Serie
TRITA-SCI-FOU ; 2019:17
Nationell ämneskategori
Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kth:diva-249387 (URN)978-91-7873-165-7 (ISBN)
Disputation
2019-05-10, FA-31, Roslagstullsbacken 21, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20190412

Tillgänglig från: 2019-04-12 Skapad: 2019-04-11 Senast uppdaterad: 2019-04-12Bibliografiskt granskad

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