On the optical properties of undoped and rare-earth-doped yttrium aluminium garnet single crystals

Varney, C. R.; Mackay, David T.; Reda, Sherif M.; Selim, F. A.

doi:10.1088/0022-3727/45/1/015103

Cited by 36 publications

(18 citation statements)

References 19 publications

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“…Figure 1(a) displays the measured optical absorption spectrum and band gap edge of two YAG single crystals grown in O 2 and H 2 . O-grown sample has the band edge at 6.5 eV, similar to YAG crystals grown in Ar atmosphere 33 and consistent with the known band gap of YAG [Ref. 32 and references therein].…”

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confidence: 78%

Hydrogen in insulating oxide Y₃Al₅O₁₂ strongly narrows the band gap

2014

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We report an unusual band gap narrowing in Y 3 Al 5 O 12 (YAG) insulating oxide after growing YAG single crystals in hydrogen atmosphere. Theory confirms that hydrogen interstitials as well as oxygen vacancies strongly shift the absorption spectrum towards lower energies. Furthermore, hydrogen eliminated all deep and shallow traps in the YAG structure and dramatically modified the optical and scintillation properties of YAG single crystals. We conclude that hydrogen plays a significant role in insulating oxides similar to its role in semiconductors and it may be used to passivate defects and improve exciton dynamics in oxides for optical and scintillation applications. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4903343]Hydrogen does not exist as a neutral impurity in semiconductors and insulators; it always gives up an electron becoming positively charged impurity or acquires an electron becoming negatively charged impurity. 1 This has profound effects on the incorporation of hydrogen in the structure and the electronic and structural properties of materials. 2,3 The importance and significance of hydrogen in materials have been revealed theoretically by Van de Walle, Zunger, their co-workers, and other groups [e.g., Refs. 1, 2, and 4-8]; and hydrogen in semiconductors has been the subject of intense investigation. 1-22 It behaves in semiconductors in two fashions. It typically acts as passivating agent reducing the electrical conductivity 3,10 and recently found that in some semiconductors, such as ZnO, SnO 2 , In 2 O 3 , and InN, hydrogen is source of doping. 2,11,12,[15][16][17]20,21 In fact, many research efforts have been carried out to control hydrogen in both amorphous and crystalline semiconductors. Meanwhile, no or little attention has been paid to the role of hydrogen in insulators. In this work, we show that incorporation of hydrogen in the Y 3 Al 5 O 12 , yttrium aluminum garnet (YAG) structure has led to significant band gap narrowing (BGN) in Y 3 Al 5 O 12 single crystals, an unusual surprising effect for hydrogen incorporation in oxides. This BGN has been confirmed by experimental and theoretical results. Furthermore, we show that hydrogen binds to native defects passivating their role as exciton traps which has remarkable impact on the optical and scintillation properties of YAG crystals. Like in semiconductors, hydrogen plays a significant role in insulating oxides and requires immediate attention, not only because hydrogen can be incorporated unintentionally as impurity into the materials and is impossible to avoid 2 but also it may provide a versatile tool to control traps and improve exciton dynamics in optical and scintillation materials. In scintillation materials, defects with deep level in the band gap may trap charge carriers and excitons preventing their transport to luminescence centers. This reduces the efficiency of luminescence and scintillation. On the other hand, defects with shallow level in the band gap trap and detrap charge carriers and excitons at room temperatu...

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confidence: 78%

Hydrogen in insulating oxide Y₃Al₅O₁₂ strongly narrows the band gap

2014

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“…The yield of fluorescent cerium ions was estimated to be at least 8%. It is believed that the yield can be significantly improved by thermal annealing in a reducing atmosphere 16 .…”

Section: Resultsmentioning

confidence: 99%

Coherent properties of single rare-earth spin qubits

et al. 2014

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Rare-earth-doped crystals are excellent hardware for quantum storage of photons. Additional functionality of these materials is added by their waveguiding properties allowing for on-chip photonic networks. However, detection and coherent properties of rare-earth single-spin qubits have not been demonstrated so far. Here we present experimental results on high-fidelity optical initialization, effcient coherent manipulation and optical readout of a single-electron spin of Ce 3 þ ion in a yttrium aluminium garnet crystal. Under dynamic decoupling, spin coherence lifetime reaches T 2 ¼ 2 ms and is almost limited by the measured spin-lattice relaxation time T 1 ¼ 4.5 ms. Strong hyperfine coupling to aluminium nuclear spins suggests that cerium electron spins can be exploited as an interface between photons and long-lived nuclear spin memory. Combined with high brightness of Ce 3 þ emission and a possibility of creating photonic circuits out of the host material, this makes cerium spins an interesting option for integrated quantum photonics.

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“…A few authors recently presented that the absorption tail of the YAG crystal between 200 and 300 nm is increased after annealing in the oxidizing atmosphere [30][31][32][33]. Varney [33].…”

Section: Introductionmentioning

confidence: 99%