Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure

Kamil Dziubek; Margherita Citroni; Samuele Fanetti; Andrew B. Cairns; Roberto Bini

doi:10.1021/acs.jpcc.7b06751

High Temperature Oxide for NVM Interpoly Dielectric Applications

MRS Proceedings ◽

10.1557/proc-532-153 ◽

1998 ◽

Vol 532 ◽

Cited By ~ 2

Author(s):

J. A. Yater ◽

B. Esho ◽

W. M. Paulson

Keyword(s):

High Temperature ◽

Flash Memory ◽

Data Retention ◽

High Quality ◽

Thermal Oxide ◽

High Temperature Oxide ◽

Conformal Coverage ◽

Temperature Oxide ◽

Edge Features ◽

Nitride Oxide

ABSTRACTHigh quality interpoly dielectrics are required for non-volatile memories (NVM) in order to achieve long term data retention and endurance over many program/erase cycles. LPCVD high temperature oxide (HTO) deposited at 800°C-900°C is investigated for use in oxide-nitride-oxide (ONO) interpoly dielectric stacks. HTO allows for reduced thermal budgets, improved conformal coverage at edge features and more flexibility in scaling the ONO stack compared to thermal oxide layers. SIMS and atomic force microscopy results indicate that smooth, high quality films are deposited with a rms roughness of 0.12nm. Etch rates of as-deposited films are lowered 35% following several densification anneals. Field strengths (at 1μA) of 7-8MV/cm and leakage currents in the pA range are measured. Centroid measurements on sressed oxides show traps to be located at the HTO/polysilicon interfaces. Finally, double poly flash memory cells fabricated with ONO stacks containing HTO top oxide show improved field strength and data retention.

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High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

10.26434/chemrxiv.8335262 ◽

2019 ◽

Author(s):

Aurelio A. Rossinelli ◽

Henar Rojo ◽

Aniket S. Mule ◽

Marianne Aellen ◽

Ario Cocina ◽

...

Keyword(s):

Quantum Dots ◽

High Temperature ◽

Equilibrium Shape ◽

Size Variation ◽

Crystal Defects ◽

Atomic Scale ◽

Quantum Yields ◽

Core Shell ◽

Compositional Gradient ◽

High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

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Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD

Nanomaterials ◽

10.3390/nano11040928 ◽

2021 ◽

Vol 11 (4) ◽

pp. 928

Author(s):

Yong Du ◽

Zhenzhen Kong ◽

Muhammet Toprak ◽

Guilei Wang ◽

Yuanhao Miao ◽

...

Keyword(s):

High Temperature ◽

Buffer Layer ◽

Layer Thickness ◽

Growth Temperature ◽

Crystalline Quality ◽

Initial Growth ◽

Two Dimensional ◽

High Quality ◽

Reduced Pressure

This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.

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Comparative Study of GaN Growth Process by MOVPE

MRS Proceedings ◽

10.1557/proc-572-463 ◽

1999 ◽

Vol 572 ◽

Author(s):

Jingxi Sun ◽

J. M. Redwing ◽

T. F. Kuech

Keyword(s):

High Temperature ◽

Comparative Study ◽

Gas Phase ◽

Residence Time ◽

Gas Flow ◽

Flow Sheet ◽

Flow Zone ◽

High Quality ◽

Phase Temperature ◽

High Temperature Gas

ABSTRACTA comparative study of two different MOVPE reactors used for GaN growth is presented. Computational fluid dynamics (CFD) was used to determine common gas phase and fluid flow behaviors within these reactors. This paper focuses on the common thermal fluid features of these two MOVPE reactors with different geometries and operating pressures that can grow device-quality GaN-based materials. Our study clearly shows that several growth conditions must be achieved in order to grow high quality GaN materials. The high-temperature gas flow zone must be limited to a very thin flow sheet above the susceptor, while the bulk gas phase temperature must be very low to prevent extensive pre-deposition reactions. These conditions lead to higher growth rates and improved material quality. A certain range of gas flow velocity inside the high-temperature gas flow zone is also required in order to minimize the residence time and improve the growth uniformity. These conditions can be achieved by the use of either a novel reactor structure such as a two-flow approach or by specific flow conditions. The quantitative ranges of flow velocities, gas phase temperature, and residence time required in these reactors to achieve high quality material and uniform growth are given.

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Carbon nitride thin films synthesized at high temperature by using RF-plasma PLD

Journal of Crystal Growth ◽

10.1016/s0022-0248(98)01109-9 ◽

1999 ◽

Vol 198-199 ◽

pp. 1028-1031 ◽

Cited By ~ 10

Author(s):

Y.K Yap ◽

Y Mori ◽

S Kida ◽

T Aoyama ◽

T Sasaki

Keyword(s):

Thin Films ◽

High Temperature ◽

Carbon Nitride ◽

Rf Plasma

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The Progress on Low-Cost, High-Quality, High-Temperature Superconducting Tapes Deposited by the Combustion Chemical Vapor Deposition Process

MRS Proceedings ◽

10.1557/proc-689-e7.8 ◽

2001 ◽

Vol 689 ◽

Author(s):

Shara S. Shoup ◽

Marvis K. White ◽

Steve L. Krebs ◽

Natalie Darnell ◽

Adam C. King ◽

...

Keyword(s):

Chemical Vapor Deposition ◽

High Temperature ◽

Critical Current Density ◽

Buffer Layer ◽

Critical Current ◽

Vapor Deposition ◽

Low Cost ◽

Chemical Vapor ◽

High Critical Current Density ◽

High Quality

ABSTRACTThe innovative Combustion Chemical Vapor Deposition (CCVD) process is a non-vacuum technique that is being investigated to enable next generation products in several application areas including high-temperature superconductors (HTS). In combination with the Rolling Assisted Biaxially Textured Substrate (RABiTS) technology, the CCVD process has significant promise to provide low-cost, high-quality lengths of YBCO coated conductor. The CCVD technology has been used to deposit both buffer layer coatings as well as YBCO superconducting layers. A buffer layer architecture of strontium titanate and ceria have been deposited by CCVD on textured nickel substrates and optimized to appropriate thicknesses and microstructures to provide templates for growing PLD YBCO with high critical current density values. The CCVD buffer layers have been scaled to meter plus lengths with good epitaxial uniformity along the length. A short sample cut from one of the lengths enabled high critical current density PLD YBCO. Films of CCVD YBCO superconductors have been grown on single crystal substrates with critical current densities over 1 MA/cm2. Work is currently in progress to combine both the buffer layer and superconductor technologies to produce high-quality coupons of HTS tape made entirely by the non-vacuum CCVD process.

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INVESTIGATION ON HIGH-TEMPERATURE OXIDIZATION OF MIRROR-QUALITY GROUND STAINLESS STEEL

International Journal of Modern Physics B ◽

10.1142/s0217979210065994 ◽

2010 ◽

Vol 24 (15n16) ◽

pp. 3005-3010 ◽

Cited By ~ 1

Author(s):

KAZUTOSHI KATAHIRA ◽

HITOSHI OHMORI ◽

MASAYOSHI MIZUTANI ◽

JUN KOMOTORI

Keyword(s):

Surface Roughness ◽

Stainless Steel ◽

High Temperature ◽

High Quality ◽

Spinel Type ◽

Combined Process ◽

Elid Grinding ◽

Modification Method ◽

Quality Surface ◽

High Quality Surface

To investigate the possibility of developing a new surface modification method by the combined process of ELID grinding and high-temperature oxidization, we treated ELID finished specimens and polished specimens by high-temperature oxidization in the atmosphere and performed detailed analysis to determine how the treatment would change the specimen surfaces. The ELID-series showed high quality surface roughness and excellent tribological characteristics as compared with the polished-series. The improved surface properties of the ELID-series seem to result from formation of fine, uniform structures of spinel-type multiple oxides FeCr 2 O 4 and Cr 2 O 3 on the surface by high-temperature oxidization.

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Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

10.26434/chemrxiv.13135136.v2 ◽

2020 ◽

Author(s):

Christiane Adler ◽

Igor Krivtsov ◽

Dariusz Mitoraj ◽

Lucía dos Santos-Gómez ◽

Santiago García-Granda ◽

...

Keyword(s):

Soft Matter ◽

High Performance ◽

Carbon Nitride ◽

Sol Gel ◽

Thin Layers ◽

Water Soluble ◽

New Paradigm ◽

High Quality ◽

Free Films ◽

Gel Processing

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for photoelectrochemical (PEC) applications, the fabrication of high-quality PCN photoelectrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of photoanodes based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor composed of nanosized (~10 nm) particles that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on a conductive substrate resulting in formation of mechanically stable porous polymeric thin layers (~400 nm), in contrast to the commonly obtained loosely attached thick particulate coatings. The resulting photoanodes exhibit unprecedented PEC performance in methanol reforming in neutral pH electrolytes with photocurrents of up to 177±27 mA cm<sup>-2</sup> (1 sun illumination) and 320±40 mA cm<sup>-2</sup> (2 sun illumination) at 1.23 V vs. RHE, maintaining such high photocurrents even down to ~0 V vs. RHE. These parameters permit effective operation even without any external electric bias, as demonstrated by bias-free photoreforming of methanol and glycerol, and highly selective (~100%) photooxidation of 4-methoxybenzyl alcohol (4-MBA). The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems, and pave the way for further applications in which high-quality PCN films are required.

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