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Article

Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films

by
Yung-Chu Liang
1,
Ching-Yin Lee
1,
Miao-I Lin
1,
Ting-En Shen
1,
Jung-Fan Hung
1,
Jien-Wei Yeh
1,2 and
Che-Wei Tsai
1,2,*
1
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300044, Taiwan
2
High Entropy Materials Center, National Tsing Hua University, Hsinchu 300044, Taiwan
*
Author to whom correspondence should be addressed.
Coatings 2024, 14(9), 1199; https://doi.org/10.3390/coatings14091199
Submission received: 15 August 2024 / Revised: 13 September 2024 / Accepted: 15 September 2024 / Published: 18 September 2024
(This article belongs to the Special Issue High Entropy Alloy Films)
Browse Figures
Versions Notes

Abstract

:
This study explores the influence of oxygen and nitrogen flow ratios on the microstructure and mechanical properties of AlCrTaTiZr high-entropy oxynitride films. Oxygen flow rates (0%–0.75%) were adjusted while maintaining a fixed nitrogen flow ratio (RN = 15%) to fabricate films with similar compositions. The results show that increasing oxygen flow enhanced hardness through solid solution strengthening and grain refinement, though excessive oxygen caused an amorphous structure and reduced hardness. After annealing at 900 °C, the hardness of all films was further increased. The film with a nitrogen flow ratio 40 times higher than oxygen exhibited the highest hardness of 21.8 GPa, along with superior mechanical performance. These findings highlight the potential of high-entropy oxynitride films for applications requiring high wear resistance and adhesion.

1. Introduction

Hard coatings have been developed since the 1970s to improve the lifetime of cutting tools [1]. Binary transition nitride films such as TiN have been widely used for their excellent properties. However, the severe oxidation of TiN at 550 °C imposes limitations on its high-temperature applications [2]. Through alloy design, the addition of aluminum has facilitated the preparation of titanium aluminum nitride (TiAlN) films [3]. Additionally, they demonstrate superior hardness, reaching an impressive 41.6 GPa [4]. Furthermore, it has been found that the addition of oxygen can improve the high-temperature properties and wear resistance of the film compared with TiAlN in the system of Ti-Al-N-O. After creating 1000 blind holes, no instances of interface failures or defects in the TiAlON coatings were observed. This suggests that the coating itself exhibits satisfactory strength [5].
High-entropy alloys (HEAs) and complex concentrated alloys (CCAs) break through the traditional thinking about multicomponent alloys [6,7]. Traditional alloy development revolves around a primary metallic element, with the addition of minute secondary elements for enhancement. In recent times, a groundbreaking shift has occurred in the composition of alloys, incorporating at least five primary elements between 5 at.% and 35 at.% [7,8]. This innovative approach not only broadens the horizons of alloy exploration but also leads to a substantial enhancement in their properties. These novel metallic alloys exhibit superior properties, such as high hardness, desirable wear resistance, oxidation resistance, irradiation resistance, and corrosion resistance [9,10,11,12,13,14]. They also offer fatigue resistance, superior ductility, and suitability for biomedical applications [15,16,17]. The superior properties of these high-entropy alloys have driven the development of high-entropy films, including high-entropy nitride and oxide films. Research on high-entropy films has primarily focused on high-entropy nitride films and high-entropy oxide films. High-entropy nitride films have demonstrated high hardness, excellent thermal stability, and superior mechanical properties. For example, (AlCrNbSiTiV)N film has a high hardness of 40 GPa and retains a face-centered cubic (FCC) structure even after being annealed at 1000 °C for 5 h [18]; (AlCrMoTaTi)N develops only a 202.0 nm oxide layer after oxidation at 1173 K for 2 h [19]. The (AlCrNbSiTiMo)N coating exhibited a low friction coefficient of approximately 0.48 at 700 °C [20]. (AlCrNbSiTi)N exhibits a low wear rate of 6.7 × 10−6 mm3·N−1·m [9]. High-entropy oxide films exhibit higher hardness than most reported oxide films and also demonstrate excellent thermal stability. For instance, (AlCrNbTaTi)O exhibits a remarkable hardness of up to 24.0 GPa [21], surpassing Al2O3 (7.2 GPa) [22], Ta2O5 (8.5 GPa) [23], and TiO2 (17 GPa) [24]. Moreover, it maintains a single-phase crystalline rutile structure even at 1200 °C [21].
The (AlCrTaTiZr)N coating exhibits an FCC crystal structure. The preference for the (111) plane orientation consequently gives rise to a surface morphology characterized by pyramid-shaped nanoclusters. Notably, the AlCrTaTiZr nitride coating demonstrates a maximum hardness of 35.2 GPa [25,26,27]. Furthermore, it can function as an effective silicon diffusion barrier, retaining thermal stability even after annealing at 800 °C for 30 min. In the presence of high temperatures, the (AlCrTaTiZr)N film exhibits a remarkable barrier to the silicon substrate, thereby demonstrating excellent heat stability [28]. On the other hand, the AlCrTaTiZr oxide film exhibits an amorphous structure, remaining non-crystalline even following annealing at 800 °C for 1 h. The hardness reaches a high value of 21.0 GPa after annealing. However, saturated oxide films exhibit a notable decrease in hardness due to the appearance of cracks on the film surface [29].
High-entropy nitride and oxide films display excellent mechanical properties, but there is a scarcity of research on high-entropy oxynitride films. In recent years, high-entropy oxynitride films have also begun to attract research interest. Kretschmer et al. demonstrated that AlCrNbTaTi high-entropy oxynitride films possess potential as diffusion barrier materials [30]. Similarly, Liu et al. analyzed the friction behavior of AlCrNbSiTiON under varying oxygen content [31]. However, despite the significant potential of high-entropy oxynitride films, research on them remains limited compared to that on high-entropy nitride films.
This study aims to investigate the microstructure and mechanical properties of high-entropy oxynitride films, an area that has received limited prior research. To achieve this, the AlCrTaTiZr equimolar high-entropy alloy is selected as the target material due to its strong affinity for nitrogen and oxygen during film deposition. By varying the nitrogen-to-oxygen flow rate ratio, the study examines how these variations affect the microstructure and mechanical properties of the resulting AlCrTaTiZr oxynitride films.

2. Materials and Methods

2.1. Sample Preparation and Film Deposition

AlCrTaTiZr high entropy oxynitride films were deposited on Si(100) wafer substrates using a DC magnetron sputtering system (Shihsin Tech Co., Taiwan, China). An equimolar AlCrTaTiZr target with two inches in diameter was prepared using vacuum arc melting. The compositional content ratio of the utilized target material is listed in Table 1. After the chamber was evacuated to a base pressure below 4 × 10−4 Pa (3 × 10−6 Torr), the substrate temperature was increased to 350 °C and then maintained for 1 h to stabilize the substrate temperature. The sputtering power was set at 150 W, with a working distance of 12 cm and a working pressure of 6.7 × 10−1 Pa (5 m Torr). The film thickness was consistently around 1 µm. The nitrogen flow ratio (RN) was fixed at 15%, while the oxygen flow ratio (RO) was decreased with the variations of RO values, namely 0%, 0.75%, 0.5%, 0.375%, and 0.1875%, denoted as L0, L1, L2, L3, and L4. The detailed deposition parameters are listed in Table 2.

2.2. Film Characterization

The chemical composition of oxynitride film was analyzed using electron probe X-ray micro-analysis (EPMA, JEOL JAX-8800, Tokyo, Japan). The crystal structures were characterized by a grazing incidence X-ray diffractometer (GIXRD, MAC Science MXP18, Tokyo, Japan) with Cu Kα radiation at a glancing-incidence angle of 1°. The scanning range of 2θ was 20° to 100°, and the scan rate was 4°/min. Scanning electron microscopy (SEM, JOEL JSM-6500F FEG-SEM, Tokyo, Japan) was used to investigate the microstructures of the surface. The hardness of the film was determined using nanoindentation (XP nanomechanical testing system, MTS Corporation, Eden Prairie, MN, USA) equipped with a diamond Berkovich indenter. In this experiment, the indentation depth does not exceed one-tenth of the film thickness to avoid substrate interference with the measured values. A load of 5 mN was applied during the indentation tests, and measurements were conducted at a total of 10 points. The average values of hardness and Young’s modulus were then calculated. The curves of X-ray photoelectron spectroscopy (XPS) were analyzed to fit various bonding after adding nitrogen using electron spectroscopy for chemical analysis (ESCA, ESCA PHI 1600, Ulvac-Phi, Chigasaki, Japan). Measurements were conducted with a base pressure of 5 × 10−9 Torr using Mg Kα radiation (1253.6 eV) at a power of 250 W. The energy resolution was 0.2 eV for the core-level spectra. An in situ 3 kV Ar+ ion gun with a 45° incidence angle was used for sample sputtering. To observe the thermal stability of this oxynitride film, samples were annealed in a rapid thermal annealing furnace pumped to 2.4 × 10−4 Pa (1.8 × 10−6 Torr). The annealing test was maintained at 900 °C for 5 h.

3. Results and Discussion

3.1. Chemical Composition

Figure 1 shows the chemical composition of the films as a function of the oxygen flow ratio when RN is fixed at 15% by EPMA. The oxygen and nitrogen contents of the film exhibit noticeable variations. Sample L1 has an oxygen content of 12.8 at.% and a nitrogen content of 35.5 at.%, while sample L2 has an oxygen content of 22.0 at.% and a nitrogen content of 31.5 at.%. As the oxygen flow ratio increases to 0.5%, the oxygen content of sample L3 rises to 28.1 at.%, surpassing the nitrogen content of 25.3 at.%. Furthermore, in sample L4, the oxygen content further increases to 35.0 at.%, while the nitrogen content decreases to 21.7 at.%. When the oxygen flow rate is 0.5% (sample L3), the ratio of nitrogen content to oxygen content in the film is similar, successfully achieving a balanced ratio of nitrogen and oxygen within the prepared oxynitride film. The reaction between metal atoms and oxygen or nitrogen atoms was explored from the perspective of heat of formation. In the AlCrTaTiZr metal system, the bonding of an oxygen atom is stronger than that of a nitrogen atom. Table 3 shows that the heat formation energy of oxides with individual metal atoms is several times higher than that for nitrides. Therefore, metal atoms tend to bond with oxygen atoms, and extremely low oxygen flow ratios were used to prepare oxynitride films in the present study.

3.2. XRD Analysis

The GIXRD diffraction patterns of films deposited under different oxygen flow ratios are presented in Figure 2. The as-deposited films exhibit an FCC structure or amorphous structure under different oxygen flow ratios in Figure 2a. It can be observed that in sample L0, with an oxygen flow rate of 0, the peak corresponds to FCC nitride. As oxygen is introduced, the structure gradually exhibits the characteristics of an amorphous phase. This trend aligns with our previous research findings, in which the structure of (AlCrTaTiZr)O films was consistently amorphous [26]. Sample L4 appears mostly in an amorphous structure due to its higher oxygen content of 35 at.% and exhibits an asymmetric diffraction pattern around 35° in the insert figure. After annealing at 900 °C for 5 h in the atmosphere in Figure 2b, sample L3 shows two sets of diffraction peaks: one for the FCC structure of the nitride with high intensity and the other for the diffraction peak of ZrO2 oxide. Upon comparing the diffraction patterns of sample L4 before and after annealing, it was found that this asymmetrical peak was contributed by the peaks of the nitride at around 36° and the oxide at around 30° in the insert figure. Furthermore, utilizing the results obtained from GIXRD, the lattice constants and grain sizes were calculated, as presented in Table 4. Both grain size and lattice constant decrease as the oxygen flow rate increases. An increase in the oxygen flow rate leads to higher ion energy, thereby enhancing ion bombardment effects. This results in more nucleation sites and a reduction in grain size. The decrease in lattice constant is caused by the substitution of smaller oxygen ions for larger nitrogen ions [35].

3.3. XPS Analysis

Additionally, XPS was employed to investigate the surface chemical states of the coatings. The XPS analysis results for each element in sample L4 are illustrated in Figure 3. The corresponding binding energies for sample L4 are provided in Table 5. The fitting curves of every branch peak can be used to compare the relative amount of each bond in the simulation. Based on the XPS results, it is evident that Al and Zr are the main elements involved in oxygen bonding, suggesting a higher propensity for oxide formation in Al and Zr. According to Table 3, a more negative formation enthalpy of the oxide indicates a stronger driving force for nucleation and growth. Therefore, due to Al and Zr having lower negative heat of formation values, they preferentially produce oxides with a higher number of bonds. However, according to the analysis results of the GIXRD crystal structure in Figure 2b, it was found that the resulting oxide structure exhibited the cubic arrangement of Zirconium Dioxide (ZrO2), which is characterized by the second lowest heat of formation. ZrO2 has a loose structure, whereas Al2O3 has a relatively complex hexagonal close-packed (HCP) corundum structure [33]. Consequently, when the heat of formation for both is nearly the same, ZrO2 is more likely to form. In comparison to other elements, the number of nitrogen and oxygen bonds for Cr, Ta, and Ti is proportionally close to each other.

3.4. Surface Morphology

The top surface and cross-section morphology of the films are shown in Figure 4. In the case of sample L0, identified as the high-entropy nitride film, a pyramid shape can be observed (Figure 4a). Due to the different growth rates between different columnar crystal planes, the faster-growing plane will inhibit the growth of other planes. Additionally, insufficient atomic kinetic energy results in a loosely packed film structure. As a result, a substantial number of triangular pyramid structures can be observed on the film’s surface. The oxygen content in the sample L1 is about 12 at.%, which has already affected the microstructure of the film. In terms of surface morphology, the pyramid shape can still be discerned in Figure 4b, but the pyramid shape is not obvious. This transformation is attributed to the addition of oxygen atoms, which results in an overall increase in system energy. This elevation in energy provides atoms with sufficient energy for migration, thereby causing the surface morphology to transition from the originally energy-deficient triangular pyramid shape to a clustered configuration (Figure 4e). From Figure 4f–j, it can be seen that there is a clear formation of a densely packed columnar grain structure in the cross-section of the film. The films exhibited a consistent presence of fine columnar grains elongated in the growth direction, maintaining this pattern uniformly throughout their entire thickness.

3.5. Mechanical Property

The mechanical property is evaluated using nanoindentation; the hardness initially increases and then decreases in Figure 5. This trend is similar to the hardness trend observed by Makino et al. for TiOxNy films prepared by ion implantation [43]. As the oxygen flow rate increases, the solid solution strengthening effect is enhanced. Additionally, according to the Hall–Petch effect, the reduction in grain size (Table 4) leads to hardness reaching its peak value of 16.0 GPa at RO = 0.5% (sample L3). However, the structure of sample L4 gradually transitions to an amorphous state, resulting in a decrease in hardness. After annealing at 900 °C for 5 h, the hardness of all samples increased, and sample L2 exhibited the largest increase, reaching 21.8 GPa. Since the atoms can be diffusive to form stable positions with strong bonds during annealing, it thus increases the Young’s modulus and the hardness. Additionally, subsequent to annealing, the hardness consistently demonstrated a trend of initially ascending and subsequently descending as the oxygen flow rate increased.
The values of H/E and H3/E2 also serve as reference indicators for mechanical properties. A high H/E ratio is generally considered to be an indication of excellent wear resistance in a coating [44], whereas a high H3/E2 ratio is generally regarded as a sign of good resistance to plastic deformation [45]. From Figure 6, it can be observed that sample L2 has the highest hardness, highest H/E value, and the highest H3/E2 value after annealing. This suggests that under identical deposition conditions, it can be expected that high-entropy oxynitride films will demonstrate superior mechanical properties compared to high-entropy nitride and oxide films. Therefore, the high-entropy oxynitride film holds significant potential for future applications in enhancing mechanical properties such as wear resistance and adhesion.

4. Conclusions

An AlCrTaTiZr high-entropy alloy target was prepared to deposit oxynitride films using DC magnetron sputtering. After annealing treatments, the effects of various nitrogen-to-oxygen flow ratios on the microstructures and mechanical properties were investigated. Due to the elevated reactivity of oxygen atoms in contrast to nitrogen atoms with metal constituents, the experimental procedure incorporated exceedingly low oxygen flow rates ranging between 0 and 0.75% while maintaining a constant nitrogen flow rate of 15%. This approach aimed to monitor the nitrogen-to-oxygen ratio throughout the fabrication process of oxynitride films and assess alterations in their microstructural features and mechanical attributes. As the nitrogen flow rate is modulated to be 30–40 times higher than the oxygen flow rate, the oxynitride films with similar nitrogen-to-oxygen composition are deposited well with lower oxygen flow ratios at RN = 15%.
When oxygen is introduced, the increased system energy causes a gradual transition in surface morphology from a loose triangular pyramid structure to a more clustered appearance. As the oxygen flow rate increases, a combination of the solid solution strengthening and the reduction in grain size leads to an increase in hardness. However, with a further increase in the oxygen flow rate, the structure in sample L4 gradually transforms into an amorphous cluster morphology, leading to a subsequent decrease in hardness. After annealing, the atoms in the film undergo rearrangement, further enhancing hardness. When oxygen is balanced with nitrogen, the resulting hardness reaches a superior value of 21.8 GPa, along with the highest H/E and H3/E2 ratios. High-entropy oxynitride films provide a new pathway for optimizing the performance of high-entropy materials. This represents a significant advancement over previous studies focused solely on nitrides or oxides, positioning high-entropy oxynitrides as promising materials for cutting-edge applications in wear-resistant coatings and adhesion improvement.
These enhancements are anticipated to contribute to future improvements in mechanical properties such as wear resistance and adhesion. By adjusting the ratio of nitrogen and oxygen flow rates, the resulting high-entropy oxynitride film demonstrates superior mechanical properties compared to both high-entropy nitride and oxide films. In conclusion, the high-entropy oxynitride film shows great promise for future applications, especially in improving mechanical properties like wear resistance and adhesion. Its unique characteristics position it as a valuable material for advancing technology and enhancing performance in various applications.

Author Contributions

Conceptualization, Y.-C.L. and M.-I.L.; methodology, M.-I.L.; validation, Y.-C.L., M.-I.L. and C.-Y.L.; formal analysis, Y.-C.L. and M.-I.L.; investigation, Y.-C.L. and C.-Y.L.; resources, J.-W.Y. and C.-W.T.; data curation, Y.-C.L., M.-I.L. and C.-Y.L.; writing—original draft preparation, Y.-C.L.; writing—review and editing, J.-W.Y., C.-W.T., C.-Y.L., J.-F.H. and T.-E.S.; visualization, Y.-C.L. and T.-E.S.; supervision, J.-W.Y. and C.-W.T.; project administration, J.-W.Y. and C.-W.T.; funding acquisition, J.-W.Y. and C.-W.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research received financial support from the “High Entropy Materials Center” as part of the Featured Areas Research Center Program, within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) and also from Project NSTC 111-2224-E-007-003, 111-2634-F-007-008, 112-2224-E-007-003 and 112-2221-E-007-032 of the National Science and Technology Council (NSTC) in Taiwan.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author, and data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Chemical composition of the films as a function of the oxygen flow ratio when RN is fixed at 15%.
Figure 1. Chemical composition of the films as a function of the oxygen flow ratio when RN is fixed at 15%.
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Figure 2. GIXRD patterns of films at various nitrogen flow ratios, as the RN is fixed at 15%: (a) as-deposited; (b) annealed at 900 °C for 5 h.
Figure 2. GIXRD patterns of films at various nitrogen flow ratios, as the RN is fixed at 15%: (a) as-deposited; (b) annealed at 900 °C for 5 h.
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Figure 3. XPS spectra of as-deposited specimens are prepared at RO = 0.75%, and the bonding fraction of each metal reacts with reactive gasses: (a) Al, (b) Cr, (c) Ta, (d) Ti, and (e) Zr.
Figure 3. XPS spectra of as-deposited specimens are prepared at RO = 0.75%, and the bonding fraction of each metal reacts with reactive gasses: (a) Al, (b) Cr, (c) Ta, (d) Ti, and (e) Zr.
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Figure 4. The top surface and cross-section morphology of the as-deposited films at different oxygen flow ratios as RN is fixed 15%; (a,f) sample L0; (b,g) sample L1; (c,h) sample L2; (d,i) sample L3; (e,j) sample L4.
Figure 4. The top surface and cross-section morphology of the as-deposited films at different oxygen flow ratios as RN is fixed 15%; (a,f) sample L0; (b,g) sample L1; (c,h) sample L2; (d,i) sample L3; (e,j) sample L4.
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Figure 5. Hardness and modulus of as-deposited and annealed films at different oxygen flow ratios.
Figure 5. Hardness and modulus of as-deposited and annealed films at different oxygen flow ratios.
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Figure 6. (a) H/E and (b) H3/E2 ratio of the as-deposited and annealed films as a function of oxygen flow ratio when RN is fixed at 15%.
Figure 6. (a) H/E and (b) H3/E2 ratio of the as-deposited and annealed films as a function of oxygen flow ratio when RN is fixed at 15%.
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Table 1. The compositional content ratio of the used target material (at.%).
Table 1. The compositional content ratio of the used target material (at.%).
AlCrTaTiZr
Nominal2020202020
Measured20.220.418.718.821.9
Table 2. Deposition parameters of various coatings.
Table 2. Deposition parameters of various coatings.
SamplesOxygen Flow Ratio, RO (%)Nitrogen Flow Ratio, RN (%)Oxygen Flow Value (sccm)Nitrogen Flow Value (sccm)
L001506
L10.1875150.0756
L20.375150.156
L30.5150.26
L40.75150.36
O2 + N2 + Ar = 40 sccm; RO = O2/40; RN = N2/40
Table 3. The heat of formation (ΔH) for nitrides and oxides for metals (kJ/mol) [32,33,34].
Table 3. The heat of formation (ΔH) for nitrides and oxides for metals (kJ/mol) [32,33,34].
NitrideΔHOxideΔH
AlN−52.0Al2O3−1117.1
CrN−40.0Cr2O3−756.5
TaN−118.0Ta2O5−816.5
TiN−155.0TiO2−944.0
ZrN−185.0ZrO2−1100.8
Table 4. Grain size of as-deposited and annealed films as a function of oxygen flow ratio (RO) when RN is 15%.
Table 4. Grain size of as-deposited and annealed films as a function of oxygen flow ratio (RO) when RN is 15%.
Sample L0L1L2L3L4
As-depositedGrain size (nm)18.8616.5314.798.48N/A
Lattice Constant (Å)4.304.284.274.25N/A
AnnealedGrain size (nm)20.2815.2313.907.658.56
Lattice Constant (Å)4.284.264.224.194.20
Table 5. XPS binding energies of sample L4.
Table 5. XPS binding energies of sample L4.
ElementsPeakBinding Energy (eV)Chemical StateReference
Al2p3/274.3Al-N (AlN)[36]
2p3/275.6Al-O (Al2O3)[36]
Cr2p3/2574.8Cr-N (CrN)[37]
2p1/2584.4[37]
2p3/2576.8Cr-O (Cr2O5)[37]
2p1/2587.2[37]
Ta4f7/223.8Ta-N (TaN)[38]
4f5/225.6[38]
4f7/227.0Ta-O (Ta2O5)[39]
4f5/228.8[39]
Ti2p3/2455.9Ti-N (TiN)[40]
2p1/2461.9[40]
2p3/2458.0Ti-O (TiO2)[41]
2p1/2464.0[41]
Zr3d5/2181.4Zr-O-N[42]
3d3/2184.0[42]
3d5/2183.0Zr-O (ZrO2)[42]
3d3/2185.8[42]
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Liang, Y.-C.; Lee, C.-Y.; Lin, M.-I.; Shen, T.-E.; Hung, J.-F.; Yeh, J.-W.; Tsai, C.-W. Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films. Coatings 2024, 14, 1199. https://doi.org/10.3390/coatings14091199

AMA Style

Liang Y-C, Lee C-Y, Lin M-I, Shen T-E, Hung J-F, Yeh J-W, Tsai C-W. Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films. Coatings. 2024; 14(9):1199. https://doi.org/10.3390/coatings14091199

Chicago/Turabian Style

Liang, Yung-Chu, Ching-Yin Lee, Miao-I Lin, Ting-En Shen, Jung-Fan Hung, Jien-Wei Yeh, and Che-Wei Tsai. 2024. "Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films" Coatings 14, no. 9: 1199. https://doi.org/10.3390/coatings14091199

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