Abstract:This article reports on two-dimensional (2D) layered hexagonal BN (h-BN) grown on sapphire by metalorganic vapor phase epitaxy (MOVPE). The highly oriented lattice and hexagonal phase of the epitaxial layers were confirmed by X-ray diffraction, Raman spectrum, and cross-section scanning transmission electron microscopy. The surface of BN over a 2-in. wafer exhibits specific 2D material morphology features for different BN thicknesses, from an atomically flat surface to a honeycomb wrinkle network. The grown ep… Show more
“…From Figure 5c we can observe the presence of graphitic-like C bonding, which is in agreement with the graphitic carbon found in Figure 4 from the early TEB sample. Other groups have published on the formation of a B-Ni alloy layer which determined the resulting film thickness [33]. Based on the fitting of the XPS data in Figure 5d, we can confirm the claim that there is the formation of B-Ni bonding when the boron precursor is exposed to the surface alone.…”
Section: Resultssupporting
confidence: 77%
“…As reported by Stehle et al [22], deviation from the 1:1 B/N ratio, caused by thermal decomposition of precursor's B-N bonds, along the length of the reactor tube can result in changes in hBN crystal shape and composition. CVD methods that utilize separate B and N precursors, like metal organic chemical vapor deposition (MOCVD), can easily overcome the issue of loss of stoichiometry and have been used successfully for growth on sapphire [33], SiC [34], and Cu [20]. Even with all the advantages of growing on Ni-lattice match, catalyst, thermal stability, etc.-there are very few reports on its use for MOCVD of hBN [35,36].…”
In this paper we demonstrate a metal organic chemical vapor deposition (MOCVD) process for growth of few layer hBN films on Ni(111) on sapphire substrates using triethylborane (TEB) and ammonia (NH3). Ni(111) was selected as a substrate due to its symmetry and close lattice matching to hBN. Using atomic force microscopy (AFM) we find hBN is well aligned to the Ni below with in plane alignment between the hBN zig zag edge and the <110> of Ni. We further investigate the growth process exploring interaction between precursors and the Ni(111) substrate. Under TEB pre-exposure Ni-B and graphitic compounds form which disrupts the formation of layered phase pure hBN; while NH3 pre-exposure results in high quality films. Tunnel transport of films was investigated by conductive-probe AFM demonstrating films to be highly resistive. These findings improve our understanding of the chemistry and mechanisms involved in hBN growth on metal surfaces by MOCVD.
“…From Figure 5c we can observe the presence of graphitic-like C bonding, which is in agreement with the graphitic carbon found in Figure 4 from the early TEB sample. Other groups have published on the formation of a B-Ni alloy layer which determined the resulting film thickness [33]. Based on the fitting of the XPS data in Figure 5d, we can confirm the claim that there is the formation of B-Ni bonding when the boron precursor is exposed to the surface alone.…”
Section: Resultssupporting
confidence: 77%
“…As reported by Stehle et al [22], deviation from the 1:1 B/N ratio, caused by thermal decomposition of precursor's B-N bonds, along the length of the reactor tube can result in changes in hBN crystal shape and composition. CVD methods that utilize separate B and N precursors, like metal organic chemical vapor deposition (MOCVD), can easily overcome the issue of loss of stoichiometry and have been used successfully for growth on sapphire [33], SiC [34], and Cu [20]. Even with all the advantages of growing on Ni-lattice match, catalyst, thermal stability, etc.-there are very few reports on its use for MOCVD of hBN [35,36].…”
In this paper we demonstrate a metal organic chemical vapor deposition (MOCVD) process for growth of few layer hBN films on Ni(111) on sapphire substrates using triethylborane (TEB) and ammonia (NH3). Ni(111) was selected as a substrate due to its symmetry and close lattice matching to hBN. Using atomic force microscopy (AFM) we find hBN is well aligned to the Ni below with in plane alignment between the hBN zig zag edge and the <110> of Ni. We further investigate the growth process exploring interaction between precursors and the Ni(111) substrate. Under TEB pre-exposure Ni-B and graphitic compounds form which disrupts the formation of layered phase pure hBN; while NH3 pre-exposure results in high quality films. Tunnel transport of films was investigated by conductive-probe AFM demonstrating films to be highly resistive. These findings improve our understanding of the chemistry and mechanisms involved in hBN growth on metal surfaces by MOCVD.
“…1. The 2D h-BN (the crystallographic phase of the grown h-BN has been demonstrated in a previous study 13 ) layer enables the release of the device and its transfer to an acrylic adhesive layer. This layer is expected to confine the heat generated by self-heating, leading to higher operating temperature of the gas sensor, which is known to contribute to an increase of the sensitivity and an improvement of the response time 2 .Figure 1Our approach for the growth, fabrication, release and transfer (see Method section for details) of boosted AlGaN/GaN gas sensor to a flexible sheet using h-BN as a buffer and release layer.
…”
The transfer of GaN based gas sensors to foreign substrates provides a pathway to enhance sensor performance, lower the cost and extend the applications to wearable, mobile or disposable systems. The main keys to unlocking this pathway is to grow and fabricate the sensors on large h-BN surface and to transfer them to the flexible substrate without any degradation of the performances. In this work, we develop a new generation of AlGaN/GaN gas sensors with boosted performances on a low cost flexible substrate. We fabricate 2-inch wafer scale AlGaN/GaN gas sensors on sacrificial two-dimensional (2D) nano-layered h-BN without any delamination or cracks and subsequently transfer sensors to an acrylic surface on metallic foil. This technique results in a modification of relevant device properties, leading to a doubling of the sensitivity to NO2 gas and a response time that is more than 6 times faster than before transfer. This new approach for GaN-based sensor design opens new avenues for sensor improvement via transfer to more suitable substrates, and is promising for next-generation wearable and portable opto-electronic devices.
“…Vapor‐phase epitaxy (VPE), is a fancy and efficient technique, which has been widely used in II–IV, II–VI conventional semiconductors . Such pleasant epitaxial growth technology can not merely effectively gain high phase‐purity nanocrystals with controlled morphology, size and orientation, but also obtain large area single‐crystal films with ultrathin thickness .…”
Inorganic cesium lead halide perovskite (CsPbX 3 , X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of highquality 2D perovskite single-crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large-scale orthorhombic CsPbBr 3 single-crystal thin films on zinc-blende ZnSe crystals are synthesized via vapor-phase epitaxy.
Structural characterizations reveal a "CsPbBr 3 (110)//ZnSe(100), CsPbBr 3 [−110]//ZnSe[001] and CsPbBr 3 [001]// ZnSe[010]" heteroepitaxial relationship between the covering CsPbBr 3 layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in-plane anisotropic absorption property from 350 to 535 nm and polarization-dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200A W −1 , a large on/off current ratio exceeding 10 4 , a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarizationdependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr 3 film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy.
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