# Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

## 2. Experimental

_{2}layer on the surface (labeled SiO

_{2}/Si). The thickness of the SiO

_{2}layer is about 300 nm. The targets used in system were alloy target containing FeCoNiCrAl and pure Al target with high purity (99.99%). The base pressure of the chamber was kept lower than 10

^{−4}Pa prior to deposition and the argon pressure was 3.8 Pa during sputtering. In order to ensure the homogeneity of the HEF, the sample stage rotated at a speed of 20 RPM. The distance and the angle between target and substrate were 105 mm and 30°, respectively. Table 1 shows the HEF samples prepared under different deposition parameters, including substrate temperature, deposition power and substrate type. Seven experiments with different targets (sample #1), different substrate temperatures (samples #2, #3 and #4), different deposition powers (samples #4 and #5) and different substrate types (samples #4, #6 and #7) were conducted. The deposition powers mentioned above were loaded to the alloy target. To adjust the proportion of elemental composition, HEF sample (sample #1) was prepared by co-sputtering with both a pure Al target and alloy target. The powers of the magnetrons were adjusted to obtain the equal atomic radio of Fe, Co, Ni, Cr and Al in preparation of sample #1.

## 3. Results and Discussion

#### 3.1. Growth Mechanism of the HEF

_{2}/Si substrate and the thickness of the SiO

_{2}is about 300 nm. Figure 1d is the enlarged image of the film and the thickness of the film measured from TEM image is 980 ± 4 nm, which is consistent with the result of SEM image. Most of the grains exhibit a columnar structure in the sample and the width of a columnar grain is related to the location. The portion of columnar grain close to the surface is wider than that close to the substrate, hence the shape of the columnar grain is like a ladder from the cross-sectional view. Besides, the partial area which is very close to the substrate has a special microstructure. The top-right inset is the enlarged image of the selected area (white box) in Figure 1d and clearly shows the difference from columnar crystal structure. Amorphous structure (located between red line and green line) and equiaxial nanocrystalline structure (located between green line and blue line) exist in this area, and columnar crystal forms above the nanocrystalline region. The width of the amorphous region and nanocrystalline region is approximately 8 nm and 20 nm respectively.

#### 3.2. The Effects of Deposition Parameters on Microstructure and Elemental Uniformity

_{2}/Si, respectively, and the power was 300 W with T = 350 °C. These two samples had little difference in their morphologies with the sample #4 which was deposited on substrate of Si (100) with a power of 300 W and substrate temperature of 350 °C. The statistical grain sizes are 89 ± 26 nm and 86 ± 23 nm, respectively, which are also close to the grain size of the sample #4. The results suggest that the structure of HEFs is almost unaffected by the crystal orientation of substrate.

_{1}, x

_{2}, …, x

_{n}) and each value of probability is [p(x

_{1}), p(x

_{2}), …, p(x

_{n})]. The Shannon information entropy of X is defined as follows:

_{i}) is the probability of occurrence of a pixel value x

_{i}. The calculated Shannon information entropies are 6.78 ± 0.28, 7.27 ± 0.22 and 6.91 ± 0.15 for samples #2, #4 and #5, respectively. The GLCM matrix is a second-order statistical method which provides information on the spatial relationships between intensities of the pixels in a given image. The entropy is calculated with the GLCM texture plugin in the software of ImageJ. The GLCM is constructed by counting the number of occurrences of a gray level adjacent to another gray level, at a specified pixel distance. Each result is divided by the total number of elements to obtain a probability. The matrix elements are the probability of the gray level co-occurrence between pixels, with the rows and columns of the matrix representing the gray levels in the image. The matrix can be computed for adjacent pixel either in horizontal (0°), vertical (90°) or diagonal (45°, 135°) direction. In our case, average values for the four directions were considered for the computed parameters. Thus, we proposed to calculate the entropy more precisely by examining the mentioned organization parameters.

#### 3.3. Mechanical Property of HEFs with Different Microstructures

_{2}/Si are 9.66 GPa and 9.59 GPa (not shown here), and both of them are close to the hardness of the sample #4.

## 4. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) SEM images of HEF from (

**a1**) plan-view and (

**a2**) cross-sectional view. (

**b**) XRD pattern of HEF showing the (110) and (211) plane with body-centered cubic (bcc) structure. (

**c**) Cross-sectional TEM image with low magnification showing the full view of the sample. (

**d**) High-magnification TEM images of HEF, and inset is the enlarged image of the white box area. The regions with different structures are separated by dotted lines. (

**e**) HRTEM image of the selected area in (

**d**) showing the detailed microstructure of the three typical regions. Insets are the corresponding FFT patterns. Some of the nanograins and columnar grains are circled by yellow dotted lines. (

**f**) Dark-field TEM image of HEF. The surface of the film and interface between film and substrate are marked in the image.

**Figure 2.**SEM images of HEF deposited with different parameters. Plan-view images for (

**a1**) RT, 300 W, on Si (100); (

**b1**) 250 °C, 300 W, on Si (100); (

**c1**) 350 °C, 300 W, on Si (100); (

**d1**) 350 °C, 100 W, on Si (100); (

**e1**) 350 °C, 300 W, on Si (110); (

**f1**) 350 °C, 300 W, on SiO

_{2}/Si. (

**a2**–

**f2**) are the corresponding cross-sectional images.

**Figure 3.**(

**a**) TEM and (

**b**) HRTEM images of HEF deposited on Si(100) at RT with a power of 300 W; (

**c**) TEM and (

**d**) HRTEM images of HEF deposited at 350 °C with a power of 300 W; (

**e**) TEM and (

**f**) HRTEM images of HEF deposited at 350 °C with a power of 100 W. The top-right insets are the low-magnification images and bottom-right insets are SAED patterns in (

**a**), (

**c**) and (

**e**), respectively. The top-right insets are FFT patterns of the selected area (red box) in (

**b**), (

**d**) and (

**f**), respectively. In figure (

**f**), the grain boundaries are marked by dotted lines.

**Figure 5.**(

**a**) SEM-EDS spectroscopy of HEF showing that the atomic radio (Fe:Co:Ni:Cr:Al) is 19.4:19.5:20.5:20.0:20.6. (

**b**) SEM image from plan-view and the corresponding SEM-EDS element mapping of the HEF. (

**c**) STEM image from cross-sectional view and the corresponding STEM-EDS element mapping.

**Figure 6.**AFM images of HEF deposited on Si (100) at (

**a**) RT, 300 W; (

**b**) 350 °C, 300 W; (

**c**) 350 °C, 100 W. The s-SNOM amplitude images of HEF deposited at (

**d**) RT, 300 W; (

**e**) 350 °C, 300 W; (

**f**) 350 °C, 100 W. The s-SNOM phase images of HEF deposited at (

**g**) RT, 300 W; (

**h**) 350 °C, 300 W; (

**i**) 350 °C, 100 W.

**Figure 7.**The hardness of HEF samples versus indentation depth. and the inset is the enlarged profile of the flat region.

Sample Number | Deposition Parameters | ||
---|---|---|---|

Power (W) | Substrate Temperature (℃) | Substrate | |

#1 | 300 _{alloy target} and 20 _{Al target} | 350 | SiO_{2}/Si |

#2 | 300 | RT | Si (100) |

#3 | 300 | 250 | Si (100) |

#4 | 300 | 350 | Si (100) |

#5 | 100 | 350 | Si (100) |

#6 | 300 | 350 | Si (110) |

#7 | 300 | 350 | SiO_{2}/Si |

**Table 2.**Full width at half maximum (FWHM) of the diffraction peak of the (110) plane and the corresponding calculated grain size for the HEFs deposited with different parameters.

Sample Number | Deposition Parameters | FWHM (°) | Grain Size (nm) | ||
---|---|---|---|---|---|

Power (W) | Substrate Temperature (℃) | Substrate | |||

#2 | 300 | RT | Si (100) | 2.54 | 3.3 |

#3 | 300 | 250 | Si (100) | 0.53 | 16 |

#4 | 300 | 350 | Si (100) | 0.32 | 27 |

#5 | 100 | 350 | Si (100) | 1.64 | 5.2 |

#6 | 300 | 350 | Si (110) | 0.33 | 26 |

#7 | 300 | 350 | SiO_{2}/Si | 0.32 | 27 |

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**MDPI and ACS Style**

Liang, Y.; Wang, P.; Wang, Y.; Dai, Y.; Hu, Z.; Tranca, D.E.; Hristu, R.; Stanciu, S.G.; Toma, A.; Stanciu, G.A.; Wang, X.; Fu, E. Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering. *Materials* **2019**, *12*, 3008.
https://doi.org/10.3390/ma12183008

**AMA Style**

Liang Y, Wang P, Wang Y, Dai Y, Hu Z, Tranca DE, Hristu R, Stanciu SG, Toma A, Stanciu GA, Wang X, Fu E. Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering. *Materials*. 2019; 12(18):3008.
https://doi.org/10.3390/ma12183008

**Chicago/Turabian Style**

Liang, Yanxia, Peipei Wang, Yufei Wang, Yijia Dai, Zhaoyi Hu, Denis E. Tranca, Radu Hristu, Stefan G. Stanciu, Antonela Toma, George A. Stanciu, Xingjun Wang, and Engang Fu. 2019. "Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering" *Materials* 12, no. 18: 3008.
https://doi.org/10.3390/ma12183008