Solid-phase epitaxy of a cavity-shaped amorphous alumina nanomembrane structure on a sapphire substrate

Jang, Jeonghwan; Yang, Dooyoung; Moon, Daeyoung; Choi, Dae Ro; Lim, Hye Jin; Kang, Sung-Gyu; Bae, Dae Kyung; Han, Heung Nam; Park, Yongjo; Yoon, Euijoon

doi:10.1016/j.jcrysgro.2018.06.012

Cited by 17 publications

(21 citation statements)

References 25 publications

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“…After PR removal using acetone, the sample was subsequently annealed at 800 °C and 1100 °C for 1 and 2 hours, respectively. During the thermal annealing, the amorphous alumina layer was crystallized into single crystalline α -phase Al 2 O 3 (same with sapphire substrate) via γ-phase Al 2 O 3 as described in our previous study 43 . Fabrication procedures of the SCES were described in detail elsewhere 34 .…”

Section: Methodsmentioning

confidence: 99%

Highly polarized photoluminescence from c-plane InGaN/GaN multiple quantum wells on stripe-shaped cavity-engineered sapphire substrate

Kim

Lee

et al. 2019

Sci Rep

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Highly polarized photoluminescence (PL) from c-plane InGaN/GaN multiple quantum wells (MQWs) grown on stripe-shaped cavity-engineered sapphire substrate (SCES) was realized. The polarization ratio was as high as 0.74 at room temperature. High-resolution X-ray reciprocal space mapping measurements revealed that the InGaN quantum wells on GaN/SCES template were under considerable anisotropic in-plane strain states of −1.178% and −1.921% along the directions perpendicular and parallel to the stripe-pattern, respectively. The anisotropic strain states were attributed to the anisotropic alignment of cavity-incorporated sapphire nano-membranes, which accommodated both anisotropic elastic relaxation in the InGaN quantum well plane as well as the graded elastic relaxation along the vertical direction in the GaN template adjacent to the InGaN/GaN MQWs. The partial strain relaxation in the InGaN wells also contributed to reduction of quantum confined Stark effect, resulting in four times higher PL intensity than InGaN/GaN MQWs on planar sapphire substrate. From theoretical calculations based on k∙p perturbation theory, it was found that fundamental origin of the polarized optical emission was strain-induced modification of valence band structures of the InGaN/GaN MQWs on the SCES. This study will allow us to realize light emitting diodes with highly polarized emission with conventional c-plane sapphire substrates by strain-induced valence band modification.

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Section: Methodsmentioning

confidence: 99%

Highly polarized photoluminescence from c-plane InGaN/GaN multiple quantum wells on stripe-shaped cavity-engineered sapphire substrate

Kim

Lee

et al. 2019

Sci Rep

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“…The width and height of the first PR pattern and the spacing between them were designed to grow a discrete micro-LED array, considering the anisotropic growth behaviors of GaN 28,29 . After the subsequent thermal treatment, the amorphous alumina nano-membrane array was crystallized into sapphire (α-phase Al 2 O 3 ) nano-membrane array by solid-phase epitaxy 25,27 , as shown in Fig. 2(g,h).…”

Section: Resultsmentioning

confidence: 99%

“…1. During the thermal annealing, the amorphous alumina nano-membrane array was crystallized into single-crystalline sapphire (α-phase) by solid-phase epitaxy, as described in detail elsewhere 25,27 . Then, a micro-LED array could be separately grown on a sapphire nano-membrane array without chip singulation process.…”

Section: Methodsmentioning

confidence: 99%

“…After the exposed amorphous alumina was etched by 85.0% H 3 PO 4 at 50 °C, all PR was removed by acetone, resulting in a cavity-incorporated alumina membrane array. The sample was subsequently annealed at 1150 °C for 2 hours in an air ambient furnace to crystallize amorphous alumina nano-membrane into single crystalline sapphire (α-phase) by solid-phase epitaxy, as described in detail elsewhere 25,27 . The sapphire nano-membrane became epi-ready states by wet cleaning and thermal treatment with rms roughness of 0.8 nm.…”

Section: Methodsmentioning

confidence: 99%

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A discrete core-shell-like micro-light-emitting diode array grown on sapphire nano-membranes

Lee

Kim

et al. 2020

Sci Rep

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A discrete core-shell-like micro-light-emitting diode (micro-LED) array was grown on a 100 nm-thick sapphire nano-membrane array without harmful plasma etching for chip singulation. Due to proper design for the sapphire nano-membrane array, an array of multi-faceted micro-LEDs with size of 4 μm × 16 μm was grown. threading dislocation density in the micro-LeD formed on sapphire nano-membrane was reduced by 59.6% due to the sapphire nano-membranes, which serve as compliant substrates, compared to GaN formed on a planar substrate. Enhancements in internal quantum efficiency by 44% and 3.3 times higher photoluminescence intensity were also observed from it. Cathodoluminescence emission at 435 nm was measured from c-plane multiple quantum wells (MQWs), whereas negligible emissions were detected from semi-polar sidewall facets. A core-shell-like MQWs were formed on all facets, hopefully lowering concentration of non-radiative surface recombination centers and reducing leakage current paths. This study provides an attractive platform for micro-LEDs by using sapphire nano-membrane.

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“…To control the morphology of more types of amorphous nanomaterials with well-defined morphology, some physical approaches, such as spinning, micro/nanocutting, and deposition, , were first investigated, and several amorphous nanomaterials with well-defined morphology were successfully fabricated, e.g., 1D Pd 40 Cu 30 Ni 10 P 20 amorphous alloy nanowires and 2D Zr-based metallic glass nanofilms . However, these physical approaches are highly dependent on expensive advanced cutting or condensing equipment, and the types (primary metallic glass) and sizes (primary hundreds of nanometers) of the products are limited.…”

Section: Introductionmentioning

confidence: 99%

Wet Chemical Synthesis of Amorphous Nanomaterials with Well-Defined Morphologies

Zhao

Wang

et al. 2021

Acc. Mater. Res.

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Conspectus Amorphous nanomaterials, with unique structural features such as long-range atomic disorder and nanoscale particle or grain sizes, possess some advantageous properties for a number of materials applications. For example, amorphous vanadium oxide exhibits a record-high cycling stability for supercapacitors. Several synthetic strategies have been developed to produce amorphous nanomaterials, such as physical processing-based approaches including cutting, deposition, and spinning, as well as chemical syntheses by solution or solid state reactions. However, despite the rapid development of amorphous nanomaterials, their morphology is still irregular or primarily sphere-like. The limited morphology control is partially attributed to the lack of preferred growth direction for the amorphous materials. It will be interesting to know whether different morphologies of even amorphous nanomaterials can influence their properties as much as their crystalline counterparts. Wet chemical synthesis, which can usually be carried out under relatively facile reaction conditions, has achieved remarkable success for creating crystalline nanomaterials with well-defined shapes, such as one-dimensional (1D) nanowires, two-dimensional (2D) nanosheets, and three-dimensional (3D) complex structures. However, there are two main obstacles for shape control of amorphous nanomaterials using wet chemical strategies. First, it is difficult to form a stable amorphous state under wet chemical conditions. The amorphous state is metastable in solution according to classic nucleation theory, which is prone to phase transformation to form crystalline state. Second, common morphology control mechanisms for nanocrystals are ultimately relying on the intrinsic directionality of the lattices, which unfortunately is not relevant to the isotropic amorphous nanomaterials. In this Account, we describe how shape control of 1D, 2D, and 3D amorphous nanomaterials can be achieved in wet chemical synthesis to create well-defined morphologies, which are based on two main strategies: Blocking agents that can stabilize the amorphous state in solution, and morphology-tunable parameters that can induce directional growth. Discussion on the phase transfer blocking mechanisms includes lattice disordering, controlled hydrolysis, rapid reaction, and ionic exchange, and for morphology control through confinement it includes precursor transformation, templated reactions, interfacial etching, and spatial confinement. In addition, we present examples showing how these well-defined morphology leads to desirable properties in applications of mechanics, energy storage, catalysis, and optics, highlighting their structural-properties relationship. Finally, some perspectives are discussed regarding future research opportunities in the area of amorphous nanomaterials.

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Solid-phase epitaxy of a cavity-shaped amorphous alumina nanomembrane structure on a sapphire substrate

Cited by 17 publications

References 25 publications

Highly polarized photoluminescence from c-plane InGaN/GaN multiple quantum wells on stripe-shaped cavity-engineered sapphire substrate

Highly polarized photoluminescence from c-plane InGaN/GaN multiple quantum wells on stripe-shaped cavity-engineered sapphire substrate

A discrete core-shell-like micro-light-emitting diode array grown on sapphire nano-membranes

Wet Chemical Synthesis of Amorphous Nanomaterials with Well-Defined Morphologies

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