Titanium Nitride Buffer Layer Research Articles

Performance enhancement of MOCVD grown Zn-doped β-Ga2O3 Deep-Ultraviolet photodetectors on silicon substrates via TiN buffer layers

Integrating β-Ga2O3-based devices on silicon substrates faces challenges due to lattice and thermal expansion mismatches, leading to performance-degrading defects. Therefore, this work explores the utilization of a titanium nitride (TiN) buffer layer in order to enhance the performance of MOCVD grown Zn-doped β-Ga2O3-based deep-ultraviolet (DUV) photodetectors (PDs) on silicon substrates with 12, 24, and 36 sccm diethylzinc (DEZn) flow rates. The XPS depth profiles revealed the presence of TiN buffer layer in β-Ga2O3/TiN/Si films, which served as a diffusion barrier during deposition, preserving interface integrity and reducing defect density. Zn-doped β-Ga2O3/TiN/Si based DUV PDs revealed remarkable results. The 12 sccm Zn-doped β-Ga2O3/TiN/Si PDs demonstrated an exceptional maximum responsivity of 31.4 A/W, which is 7 times higher compared to the undoped β-Ga2O3/TiN/Si (4.47 A/W) under a 5 V bias and 240 nm wavelength illumination. This PD exhibited the detectivity of 1.68 × 1013 Jones and EQE of 1.63 × 104 %. This PD possess quick rise time of 6.5 s and fall time of 0.5 s. The energy band diagram for Zn-doped β-Ga2O3/TiN/Si metal–semiconductor-metal type PDs is discussed. This work demonstrates that TiN buffer layers and Zn doping significantly improve the performance and reliability of β-Ga2O3-based DUV photodetectors on silicon substrates.

Interface engineering in epitaxial growth of sputtered β-Ga2O3 films on Si substrates via TiN (111) buffer layer for Schottky barrier diodes

The native amorphous silicon oxide (SiO2) layer formed on the Si substrate leads to the (100) preferred orientation for β-phase gallium oxide (β-Ga2O3), which encounters various defects in β-Ga2O3, such as twin boundaries and stacking faults etc. The (111) preferred orientation of titanium nitride (TiN) hetero-buffer layer can be used in the interface between β-Ga2O3 and Si substrates to reduce the lattice mismatch between them and increase the (˗201) preferred orientation for β-Ga2O3. The lattice mismatch between TiN (111) and β-Ga2O3 (˗201) is 0.76%, which is less than the β-Ga2O3 (˗201)/Si (111) about ˗6.3%. The β-Ga2O3 and TiN films were grown using radio-frequency magnetron sputtering on Si substrates, which possess polycrystalline nature as revealed using X-ray diffraction patterns and high-resolution transmission electron micrographs. The optimal parameters are found as, process atmosphere: Ar = 10 sccm, RTA: 800 °C for β-Ga2O3/TiN (300 nm)/Si. This work highlights the effect of the TiN hetero-buffer layer, the process atmosphere, and annealing temperatures on the microstructural and surface morphology of β-Ga2O3 films. The lateral Schottky barrier diode (SBD) were fabricated using the optimized β-Ga2O3/TiN (300 nm)/Si film. The Baliga's Figure of Merit (BFOM) of the lateral SBD is 7.60 × 10−2 kW/cm2, which exhibits 4 order of BFOM higher than that of β-Ga2O3/Si SBD due to interface engineering. The β-Ga2O3/TiN (300 nm)/Si hetero-structure demonstrates a promising material to be employed in the next generation β-Ga2O3 based power devices.

Integration and structural analysis of strain relaxed bi-epitaxial zinc oxide(0001) thin film with silicon(100) using titanium nitride buffer layer

Epitaxial growth of c-plane ZnO(0001) has been demonstrated on the Si(001) by using TiN as an intermediate buffer layer. Because of different out of plane symmetry of the substrate (Si/TiN) and the film (ZnO), two orientations of ZnO domains were obtained and the ZnO film growth is of bi-epitaxial nature. The ZnO thin film was observed to be nearly strain relaxed from X-ray and Raman measurements. The interface between the ZnO and TiN was investigated by transmission electron microscopy, and atomic arrangement has been modeled to understand the crystallographic orientation and structure of the domain/grain boundaries. Reaction at ZnO/TiN interface at higher growth temperature causing zinc titanate formation was observed. The grain boundary structure between the observed domains investigated by scanning transmission electron microscopy, revealed the ZnO(0001) planes to be contiguous across the grain boundary which is significant from the perspective of conduction electron scattering. In this configuration, the TiN (being electrically conductive) can be effectively used as an electrode for novel vertically integrated device applications (like light emitting diodes) directly on Si(100) substrate.

Enhancement of near-band edge photoluminescence of ZnO film buffered with TiN

ZnO films were deposited on Si substrate by RF-sputtering using titanium nitride (TiN) as buffer layer that was deposited at different thicknesses: 160 and 2290nm. Despite the lattice mismatch of up to 6.35% between ZnO and TiN, the ZnO films deposited on TiN buffer layers show enhanced near-band-edge photoluminescence (PL) emission at room temperature which is two times higher of magnitude than those grown directly on Si. The PL enhancement intensity, provided by TiN buffer introduction, is attributed to the improvement of ZnO crystalline quality and stoichiometry. The use of a good electrical conductor which has high thermal stability like TiN as buffer layer for the blue emission enhancement of ZnO would make it promising for optoelectronic applications.

A sensitive enzymeless hydrogen-peroxide sensor based on epitaxially-grown Fe 3O 4 thin film

A novel and facile approach has been developed to synthesize thin films of magnetite (Fe 3O 4) with epitaxial needle-like columnar grains on titanium nitride (TiN) buffered substrate using DC magnetron reactive sputtering. TiN buffer layer was first sputtered onto a substrate at 550 °C as a preferable substrate for growth following sputtering of epitaxial crystalline Fe 3O 4 at 300 °C. The as-synthesized epitaxial Fe 3O 4 was extensively characterized. The electrocatalytic activity of the epitaxial Fe 3O 4 thin-film sensor against hydrogen peroxide (H 2O 2) reduction was rapid with a response time less than 5 s. The sensor also exhibited an acceptable stability, a satisfying sensitivity of 432.2 μA mM −1 cm −2, good specificity to the substrate, a dynamic working range of up to 0.7 mM and a low detection limit of 1.0 μM. The sensor performance correlated well ( R 2 = 0.996) with results obtained using a commercial HPLC-UV device. The sensor performance was robust and accurate in measuring H 2O 2 in some complex matrices. The advantages of relative simplicity and ease of mass production make the epitaxial Fe 3O 4 thin film promising candidate for use in sensing applications.

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti–29Nb–5Zr alloy for biomaterials

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti–29Nb–5Zr alloy for biomaterials have been investigated by several experimental methods. The nanotubular structure was formed by anodizing the Ti–29Nb–5Zr alloy in 1M H3PO4 electrolytes with 1.0wt.% NaF at room temperature. Hydroxyapatite (HA)/titanium nitride (TiN) films were deposited on Ti–29Nb–5Zr alloy specimens using a magnetron sputtering system. The HA target was made of human tooth-ash by sintering at 1300°C for 1h, and the HA target had an average Ca/P ratio of 1.9. The HA/TiN depositions were performed, using the pure HA target, on Ti–29Nb–5Zr alloy following the initial deposition of a TiN buffer layer coating. Microstructures and nanotubular morphology of the coated alloy specimens were examined by FE-SEM, EDX, XRD, and XPS. The Ti–29Nb–5Zr alloy substrate had small grain size and preferred orientation along the drawing direction. The HA/TiN coating was stable with a uniform morphology at the tips of the nanotubes.

Interface analysis of CVD diamond on TiN surfaces

We prepared polycrystalline diamond thin films on smooth silicon substrates with the help of a titanium nitride (TiN) buffer layer. TiN layers of different thickness were deposited first on crystalline silicon substrates with mirror finish. The TiN layers were placed by physical vapor deposition (PVD) assisted by direct current reactive magnetron sputtering. Later, diamond thin films were grown by hot filament chemical vapor deposition (HF-CVD). Scanning electron microscopy observations show a notable increase in the size of diamond particles on the substrates with the TiN buffer layer, as opposed to the plain, only scratched substrates. The diamond films were characterized by high-resolution transmission electron microscopy (HRTEM), electron energy loss (EELS) and energy dispersive spectroscopies (EDS). A buffer layer ∼0.8 nm thick is observed between the diamond particles and the TiN layer. EDS experiments reveal a carbon nitride compound at the interphase. There is no evidence of degradation (cracking, delamination, etc.) of the TiN layers for thickness below 0.5 μm.

Pulsed Laser Deposition and Characterization of Novel Cu/TiN/Si(100) Heterostructures Grown VIA Domain Epitaxy

Laser physical vapor deposition (LPVD) has been used to study the growth morphology of copper thin films on siliconi 100) substrates with epitaxially grown titanium nitride buffer layers. The epitaxial TiN film was grown on hydrogen-terminated Si substrate at 600°C. The Cu films were grown on TiN/Si at different substrate temperatures ranging from room temperature to 600°C in vacuum (∼10-7 torr) with a pulsed KrF excimer laser (τ = 248 nm, ι = 25 ns). The pulse repetition rates were 15 and 30 Hz. The X-ray diffraction (XRD) results indicate that below 200°C, the Cu film has a mosaic spread of (001) textures of about 2.3° and that a small fraction (0.05 ) is of (111) textures. But above 200°C there is only (001) textures Cu of about 0.42° to 0.40° depending on the substrate temperature (200° - 600°C). The Rutherford backscattering (RBS) spectra show that the TiN has a yield (xmin) of 13.5 % whereas that for Cu is 70 %. A detail high resolution transmission electron microscopy (HRTEM) was performed to reveal the growth morphology of Cu films with substrate temperature. It was observed that at 15 Hz, Cu grows three-dimensionally on TiN with the island sizes ranging from 0.3–1.5 μm depending upon the substrate temperature. All of these islands grow epitaxially on TiN giving rise to Cu ║ TiN ║ Si. At 30 Hz, there is a uniform growth of epitaxial cube-on-cube Cu film on TiN/Si. The Cu/TiN and TiN/Si interfaces are quite abrupt with absolutely no indication of interfacial reactions between them. Moire fringe spacings suggest that both TiN and Cu unit cells are completely relaxed. Although there exist a large lattice misfit between Cu and TiN (15.8%) and as well as between TiN and Si (24.6%), it has been possible to grow epitaxial Cu/TiN/Si(100) heterostructures by means of domain epitaxial growth. In this case, there are 4-to-3 match in unit cells for TiN/Si structure and 7-to-6 match for Cu/TiN structure giving rise to remaining lattice misfits of only 4.0% and 0.6% respectively.

Pulsed laser deposition of Y1Ba2Cu3O7- delta films on polycrystalline metallic substrates with TiN buffer layers

Deposition of high-quality Y1Ba2Cu3O7- delta (YBCO) thin films on technologically important substrates such as stainless steel or high-temperature structural Ni-based superalloys is a difficult problem due to inherent interdiffusion problems between substrates and superconducting overlayers. To overcome this difficulty the concept of the buffer layer has been utilized and good quality YBCO thin films have been fabricated on Hastelloy (C), Inconel (600) and stainless steel (304) with titanium nitride (TiN) buffer layers. TiN is an excellent choice as a barrier layer on these metallic substrates due to low diffusivity, high thermal stability and thermal coefficient of expansion matching with the substrates. Because of the matching of the thermal expansion coefficient of TiN ( approximately (8.0-9.0)*10-6 K-1) with substrates ( approximately (9-10)*10-6 K-1) and YBCO ( approximately (12-13)*10-6 K-1) and its diffusion barrier characteristics, good quality high-Tc films have been grown on all substrates by single-chamber in situ laser processing at 600 degrees C. The films were characterized by X-ray diffraction, four-point AC electrical resistivity, scanning electron microscopy and Auger electron spectroscopy (AES) techniques. AES depth profiling indicated no interdiffusion of Fe across the interface of TiN and substrates. c-axis-oriented good quality thin films (zero resistance above liquid nitrogen temperature and Jc approximately 104-105 A cm-2 at 77 K) were obtained on these substrates. Optimization of laser deposition parameters to obtain superconducting thin films on metallic substrates for practical applications will be discussed in this paper.

Enhancement in critical current density of Y1Ba2Cu3O7−δ thin films on hastelloy with TiN buffer layers

We have prepared high quality superconducting Y1Ba2Cu3O7−δ (YBCO) thin films on hastelloy (C) with titanium nitride (TiN) buffer layers. The hastelloy (C) is a nickel based superalloy with excellent high-temperature properties and corrosion resistance. The superconducting and TiN buffer layers were deposited sequentially at 600 °C using pulsed excimer laser irradiation of the respective targets. TiN has been suitably chosen owing to matching of thermal expansion coefficient (∼8.0–9.0×10−6/K) with hastelloy (∼9.0×10−6/K) and YBCO (∼12–13×10−6/K). X-ray diffraction, four point ac electrical resistivity and scanning electron microscope studies were performed on these films for correlations between crystal structure, microstructure, and superconducting properties. Auger electron spectroscopy (AES) was used to determine the extent of interdiffusion in metal-TiN and TiN-Y1Ba2Cu3O7−δ interfaces. These films exhibited a characteristic metallic conductivity followed by an onset of superconductivity at 91 K with a zero resistance temperature (Tco) of 85 K. Critical current density (Jc) for these films (77 K and zero magnetic field) was determined to be ∼9.0×104 A/cm2 for thin films on metallic substrates.