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1. Processing of diamond films with azimuthal texture on silicon wafer for quantum systems

   https://doi.org/10.1557/s43578-023-01273-6  

   Jayaseelan, Vidhya Sagar ; Singh, Raj N ( March 2024 , Journal of Materials Research)

   Ramamoorthy, Ramesh (Ed.)

   Diamond is a wide bandgap semiconductor possessing unique properties for applications in quantum systems and ultra-wide bandgap electronics, which require a fundamental understanding of processing of high-quality diamond crystals and textured films by microwave plasma-enhanced chemical vapor deposition (MPECVD). The approach of bias-enhanced nucleation (BEN) followed by growth is studied for the processing of oriented diamond film with azimuthal texture. The magnitude of the applied electric field is shown to play an important role in the processing of the highly azimuthally textured diamond film on Si (100) substrate. The X-ray diffraction pole figure, scanning electron microscopy, and Raman spectroscopy results show that an optimum applied electric field during BEN and microwave plasma conditions leads to the formation of diamond film with azimuthal texture upon growth by MPECVD. These results are promising for fabricating diamond films of optimum characteristics containing nitrogen-vacancy (NV) defect centers for application in quantum devices. 

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2. Preferentially oriented growth of diamond films on silicon with nickel interlayer

   https://doi.org/10.1007/s42452-022-05092-y  

   K.C., Anupam ; Siddique, Anwar ; Anderson, Jonathan ; Saha, Rony ; Gautam, Chhabindra ; Ayala, Anival ; Engdahl, Chris ; Holtz, Mark W. ; Piner, Edwin L. ( July 2022 , SN Applied Sciences)

   A multistep deposition technique is developed to produce highly oriented diamond films by hot filament chemical vapor deposition (HFCVD) on Si (111) substrates. The orientation is produced by use of a thin, 5–20 nm, Ni interlayer. Annealing studies demonstrate diffusion of Ni into Si to form nickel silicides with crystal structure depending on temperature. The HFCVD diamond film with Ni interlayer results in reduced non-diamond carbon, low surface roughness, high diamond crystal quality, and increased texturing relative to growth on bare silicon wafers. X-ray diffraction results show that the diamond film grown with 10 nm Ni interlayer yielded 92.5% of the diamond grains oriented along the (110) crystal planes with ~ 2.5 µm thickness and large average grain size ~ 1.45 µm based on scanning electron microscopy. Texture is also observed to develop for ~ 300 nm thick diamond films with ~ 89.0% of the grains oriented along the (110) crystal plane direction. These results are significantly better than diamond grown on Si (111) without Ni layer with the same HFCVD conditions. The oriented growth of diamond film on Ni interlayers is explained by a proposed model wherein the nano-diamond seeds becoming oriented relative to the β₁-Ni₃Si that forms during the diamond nucleation period. The model also explains the silicidation and diamond growth processes.

   High quality diamond film with minimum surface roughness and ~93% oriented grains along (110) crystallographic direction is grown on Si substrate using a thin 5 to 20 nm nickel layer.

   A detailed report on the formation of different phases of nickel silicide, its stability with different temperature, and its role for diamond film texturing at HFCVD growth condition is presented.

   A diamond growth model on Si substrate with Ni interlayer to grow high quality-oriented diamond film is established.

    

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3. Fabrication of Q-Carbon Nanostructures, Diamond and Their Composites with Wafer-Scale Integration

   https://doi.org/10.3390/cryst12050615  

   Khosla, Nayna ; Narayan, Jagdish ( May 2022 , Crystals)

   We report the formation of Q-carbon nanolayers, Q-carbon nanoballs, nanodiamonds, microdiamonds, and their composites by controlling laser and substrate variables. The choice of these parameters is guided by the SLIM (simulation of laser interactions with materials) computer modeling. For a constant film thickness and initial sp3 content, we obtain different microstructures with increasing pulse energy density as a result of different quenching rate and undercooling. This is related to decreasing undercooling with increasing pulse energy density. The structure of thin film Q-carbon evolves into Q-carbon nanoballs with the increase in laser annealing energy density. These Q-carbon nanoballs interestingly self-organize in the form of rings with embedded nanodiamonds to form Q-carbon nanoballs/diamond composites. We form high quality, epitaxial nano, and micro diamond films at a higher energy density and discuss a model showing undercooling and quenching rate generating a pressure pulse, which may play a critical role in a direct conversion of amorphous carbon into Q-carbon or diamond or their composites. This ability to selectively tune between diamond or Q-carbon or their composites on a single substrate is highly desirable for a variety of applications ranging from protective coatings to nanosensing and field emission to targeted drug delivery. Furthermore, Q-carbon nanoballs and nanodiamonds are utilized as seeds to grow microdiamond films by HFCVD. It is observed that the Q-carbon nanoballs contain diamond nuclei of critical size, which provide available nucleation sites for diamond growth, leading to stress-free, adherent, and denser films, which are needed for a variety of coating applications. 

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4. Comparison of Hafnium Dioxide and Zirconium Dioxide Grown by Plasma-Enhanced Atomic Layer Deposition for the Application of Electronic Materials

   https://doi.org/10.3390/cryst10020136  

   Xiao, Zhigang ; Kisslinger, Kim ; Chance, Sam ; Banks, Samuel ( February 2020 , Crystals)

   We report the growth of nanoscale hafnium dioxide (HfO2) and zirconium dioxide (ZrO2) thin films using remote plasma-enhanced atomic layer deposition (PE-ALD), and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using the HfO2 and ZrO2 thin films as the gate oxide. Tetrakis (dimethylamino) hafnium (Hf[N(CH3)2]4) and tetrakis (dimethylamino) zirconium (IV) (Zr[N(CH3)2]4) were used as the precursors, while O2 gas was used as the reactive gas. The PE-ALD-grown HfO2 and ZrO2 thin films were analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The XPS measurements show that the ZrO2 film has the atomic concentrations of 34% Zr, 2% C, and 64% O while the HfO2 film has the atomic concentrations of 29% Hf, 11% C, and 60% O. The HRTEM and XRD measurements show both HfO2 and ZrO2 films have polycrystalline structures. n-channel and p-channel metal-oxide semiconductor field-effect transistors (nFETs and pFETs), CMOS inverters, and CMOS ring oscillators were fabricated to test the quality of the HfO2 and ZrO2 thin films as the gate oxide. Current-voltage (IV) curves, transfer characteristics, and oscillation waveforms were measured from the fabricated transistors, inverters, and oscillators, respectively. The experimental results measured from the HfO2 and ZrO2 thin films were compared. 

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5. Effects of Silicon Content on the Microstructures and Mechanical Properties of (AlCrTiZrV)-Six-N High-Entropy Alloy Films

   https://doi.org/10.3390/e21010075  

   Niu, Jingrui ; Li, Wei ; Liu, Ping ; Zhang, Ke ; Ma, Fengcang ; Chen, Xiaohong ; Feng, Rui ; Liaw, Peter ( January 2019 , Entropy)

   A series of (AlCrTiZrV)-Six-N films with different silicon contents were deposited on monocrystalline silicon substrates by direct-current (DC) magnetron sputtering. The films were characterized by the X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and nano-indentation techniques. The effects of the silicon content on the microstructures and mechanical properties of the films were investigated. The experimental results show that the (AlCrTiZrV)N films grow in columnar grains and present a (200) preferential growth orientation. The addition of the silicon element leads to the disappearance of the (200) peak, and the grain refinement of the (AlCrTiZrV)-Six-N films. Meanwhile, the reticular amorphous phase is formed, thus developing the nanocomposite structure with the nanocrystalline structures encapsulated by the amorphous phase. With the increase of the silicon content, the mechanical properties first increase and then decrease. The maximal hardness and modulus of the film reach 34.3 GPa and 301.5 GPa, respectively, with the silicon content (x) of 8% (volume percent). The strengthening effect of the (AlCrTiZrV)-Six-N film can be mainly attributed to the formation of the nanocomposite structure. 

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