I 20 6: Tainan

International Conference on Ion Implantation Technology

Committee Members

International Committee

Dr. Robert Brown retired USA

Dr. David Chivers Ion Links UK

Prof. Paul Chu H.K. City University PRC

Dr. Michael I. Current Current Scientific USA

Dr. Susan Felch consultant USA

Prof. Russell Gwilliam U. Surrey UK

Dr. Amitabh Jain Global Foundries USA

Prof. Kevin S. Jones University of Florida USA

Dr. Masataka Kase Socio next Japan

Dr. Lawrence A. Larson Texas State University USA

Prof. Jira Matsuo Kyoto University Japan

Dr. Dirk Mous High Voltage Engineering Holland

Masao Naito Nissin Ion Japan

Prof Lourdes Pelez U Valladolid Spain

Dr. Tony Renau Applied Materials USA

Dr. Peter Rose retired USA

Dr. Lenny Rubin Axcelis USA

Dr. Geoffrey Ryding GTAT USA

Prof. Heiner Ryssel Fraunhofer Institute Germany

Dr. Werner Schustereder Infineon Austria

Prof. Ed Seebauer University Illinois USA

Dr. Sugitani Sumitomo ion Technology Japan

Dr. Mikio Takai Osaka University Japan

Dr. Mitch Taylor consultant USA

Frank Torregrossa Ion Beam Services France

Aaron Vanderpool Intel USA

Dr. Anatoli Vyatkin Russian Academy of Science Russia

Dr. Zhimin Wan AIBT Taiwan

Prof. lsao Yamada Hyogo University Japan

Dr. James Ziegler retired USA

2

' -

Technical Program Committee

Paul Chu Hong Kong City University PRC Benjamin Columbeau Applied Materials USA Michael Current Current Scientific USA Ray Duffy Tyndall Institute Ireland Susan Felch consultant USA Genshu Fuse Sumitomo Ion Technology Japan Russell Gwilliam University Surrey UK Amitabh Jain Global Foundries USA Causon Jen Axcelis Taiwan Masataka Kase Socio next Japan Fareen Adeni Khaja Applied Materials USA Wilfried Lerch Centrotherm Germany Jiro Matsuo Kyoto University Japan Steve Moffatt Applied Materials UK Masao Naito Nissin Ion Japan Lourdes Pelez University Valladolid Spain Leonard Rubin Axcelis USA Ed Seebauer University Illinois USA Michiro Sugitani Sumitomo Ion Technology Japan Kyoichi Suguro Toshiba Japan Paul Timans Thermal Process Solutions UK Wilfried Vandervorst IMEC Belgium lsao Yamada Hyogo University Japan

Affairs Chair

Tai-Chen Kuo National Cheng Kung University Taiwan

Excursion Chair

Tzu-Lang Shih National Cheng Kung University Taiwan

Treasurer

Wan-Yu Shih National Cheng Kung University Taiwan

3

20

Invited SpeechSeptember 27, 2016

09:00-09:30

Justin Holmes

Univ. College Cork, Ireland

“Chemical Approaches for Doping Semiconductor

Nanostructures”

09:30-10:00

Zengfeng Di

SMIT, China

“Ion Beam Synthesis Of Layer-Tunable And Bandgap-tunable

Graphene”

13:30-14:00

Paul Chu

City Univ. of Hong Kong, Hong Kong

“Modification of Biomaterials and Biomedical Devices by Plasma

Immersion Ion Implantation & Deposited and Related

Techniques”

September 28, 2016

09:10-09:40

Ling-Yen Yeh

Taiwan Semiconductor Manufacturing Co., Taiwan

“An investigation of spike-RTA-driven non-uniformity in

transistors”

Modification of Biomaterials and Biomedical Devices by Plasma

Immersion Ion Implantation & Deposited and Related Techniques

Paul K Chu*

Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon,

Hong Kong, China

The interactions between biomaterials and living tissues are crucial to clinical success and on

account of increasing clinical demands, biomaterials and biomedical implants are constantly

refined both in sophistication and diversity. Since most biomaterials having the favorable bulk

properties such as durability, strength, hardness, and chemical inertness may not perform the

pre-designed biological functions, surface modification is frequently conducted. Plasma-based

technology offers the unique capability that certain surface properties can be selectively modified

to cater to the biological requirements while desirable bulk properties of the materials such as

those mentioned above can be retained. In particular, plasma immersion ion implantation and

deposition (PIII&D) is widely used in the surface treatment of functional materials and industrial

implants including biomaterials and biomedical implants because it is a non-line-of-sight

technique and especially suitable for biomedical devices with a complex geometry such as

orthopedic implants, bone fixation devices, scoliosis correction rods, cardiovascular stents, and

artificial heart valves. In this invited talk, recent research performed in the Plasma Laboratory of

City University of Hong Kong pertaining to plasma surface treatment of biomaterials and

biomedical devices will be described. Examples include nanostructured coatings/surfaces,

biodegradable metals and polymers, bacteria resistance, and surface biocompatibility.

Keywords: plasma; ion beam; surface modification; biomaterials

21

Modification of Biomaterials and Biomedical Devices by Plasma Immersion Ion Implantation & Deposition

and Related Techniques

Paul K Chu Department of Physics and Materials Science

City University of Hong Kong Tat Chee Avenue, Kowloon, Hong Kong, China

paul.chu@cityu.edu.hk

Abstract—The interactions between biomaterials and living tissues are crucial to clinical success and on account of increasing clinical demands, biomaterials and biomedical implants are constantly refined both in sophistication and diversity. Since most biomaterials with favorable bulk properties such as durability, strength, hardness, and chemical inertness may not perform the pre-designed biological functions, surface modification is frequently conducted. Plasma-based technology offers the unique capability that certain surface properties can be selectively modified to cater to the biological requirements while desirable bulk properties of the materials such as those mentioned above can be retained. In particular, plasma immersion ion implantation and deposition (PIII&D) is widely used in the surface treatment of functional materials and industrial implants including biomaterials and biomedical implants because being a non-line-of-sight technique, it is especially suitable for biomedical devices with a complex geometry such as orthopedic implants, bone fixation devices, scoliosis correction rods, cardiovascular stents, and artificial heart valves. In this invited talk, recent research performed in the Plasma Laboratory of City University of Hong Kong pertaining to plasma surface treatment of biomaterials and biomedical devices is reviewed.

Keywords—plasma; ion beam; surface modification; biomaterials

I. TITANIUM NITRIDE

Transition metal nitrides are often used as protective coatings in the industry and in particular, titanium nitride (TiN) has desirable mechanical and biological properties [1]. However, bacterial infection remains one of the serious complications after surgery and it may be difficult to treat and require removal of the failed biomedical implants [2]. Hence, it is important that biomedical implants have the intrinsic long-term antimicrobial ability to combat infection and optimize healing in vivo. Silver (Ag) is an effective antibacterial agent capable of killing antibiotic-resistant bacteria [3]. However, the effects of Ag on the other biological properties of TiN such as cyto-compatibility need to be clarified. In our recent

experiments, Ag is plasma-implanted into 100 nm thick TiN films deposited on silicon by magnetron sputtering and the surface properties and cyto-compatibility are studied [4]. After Ag PIII, many fine TiN particles are observed from the surface and the hydrophilic properties are improved slightly although it is still hydrophobic. The hardness of the TiN film is about 20 GPa and does not change significantly after Ag PIII. Hence, the good mechanical properties of the materials are preserved. In the cell culture experiments, as shown in Fig. 1, osteoblasts seeded on the PIII sample exhibit a polygonal shape and cover a large area thus indicating good cell attachment and even better cell proliferation than the un-implanted sample.

Fig. 1. Morphology of the seeded osteoblasts after culturing for 24 h: (a) Ag-PIII sample, (b) Enlarged image of (a), (c) TiN sample, and (d) Enlarged image of (d).

In prior studies of the biological roles played by rare-earth elements such as praseodymium, scandium, and lanthanum, soluble salts (citrate or chloride) are normally introduced into the animals by injection or ingestion [5]. Although the direct biological role of praseodymium compounds is still controversial, ion implantation of Pr into artificial biomedical

978-1-5090-2024-9/16/$31.00 ©2016 IEEE

implants is potentially useful. Hence, we have investigated the blood and cyto-compatibiliy of TiN implanted with praseodymium [6]. Electrical measurements disclose that the corrosion resistance of the Pr-implanted TiN coatings in blood plasma is improved. Furthermore, Pr ion implantation reduces the hemolysis rate suggesting their suitability in cardiovascular applications. The viability of vascular endothelial cells seeded on the un-implanted TiN control as well as TiN coatings implanted with Pr for different time is evaluated. As shown in Fig. 2, the vascular endothelial cells attach and grow to confluence on the Pr ion-implanted TiN coatings and a network composed of vascular tissues is observed from the 0.5 h Pr implanted sample. The data reveal that Pr ion implantation improves the corrosion resistance and cyto-compatibility of TiN coatings in blood plasma.

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 2. Morphology of endothelial cells after culturing for 1 day: (a) Un-implanted TiN coating, (b) 0.5 h Pr ion-implanted TiN coating, and (c) 1 h Pr ion-implanted TiN coating; Cell morphology after culturing for 6 days: (d) Un-implanted TiN coating, (e) 0.5 h Pr ion-implanted TiN coating showing acvascular tissue-like network in vitro, and (f) 1 h Pr ion-implanted TiN coatings [6].

II. MAGNESIUM AND MAGNESIUM ALLOYS

In addition to being common structural materials in automobiles, electronics, and aerospace components, magnesium and magnesium alloys are degradable biomaterials but their rapid corrosion rates in the physiological environment adversely affect tissue healing in vivo [7]. Surface passivation is a viable approach to mitigate the corrosion rate, but the high affinity of magnesium to oxygen makes it difficult to select the appropriate reactive elements to passivate the surface. Therefore, it is preferable to select an element that forms an oxide layer on magnesium spontaneously in order to construct a barrier to retard corrosion. Rare-earth elements are potential candidates and in our study, Pr is implanted into pure magnesium and AZ80 magnesium alloy and the corrosion resistance in artificial hand sweat is evaluated [8].

Fig. 3a shows the polarization curves of the implanted and un-implanted samples and Fig. 3b shows the corrosion potential and corrosion current density obtained from the

polarization curves by cathodic Tafel fitting. The curves of the Pr ion-implanted samples shift towards a smaller current density and nobler potential and the corrosion current density of the Pr ion-implanted magnesium diminishes from 1.32 × 10−4 to 7.96 × 10−5 A/cm2 and that of the Pr ion-implanted AZ80 alloy decreases from 3.54 × 10−4 to 1.11 × 10−5 A/cm2. A larger reduction in the corrosion current density is observed from the AZ80 alloy than the pure magnesium sample. A smaller corrosion current density indicates higher corrosion resistance and hence, Pr ion implantation has a retarding effect on corrosion. Different surface morphologies are observed from the two samples. Block-like products and many cracks indicative of corrosion are observed from the pure magnesium and untreated AZ80 alloy. In contrast, only some pits from weak regions appear on the Pr-implanted samples and fewer areas show damage. The results provide evidence that the surface corrosion resistance is significantly improved by the formation of a praseodymium-rich oxide film.

Fig. 3. (a) Polarization curves; (b) Corrosion potential and corrosion current density obtained from the polarization curves by cathodic Tafel fitting; (c) Surface morphology of the samples after immersion in artificial hand sweat for 60 min [8].

Neodymium in the RE WE43 magnesium alloy improves the mechanical properties by grain boundary strengthening as a result of the formation of a intermetallic phase in the grain boundaries [9] and improves the corrosion resistance of magnesium alloys due to suppression of galvanic effects by the intermetallic compounds and surface layer containing neodymium oxide [10]. It is also biocompatible as relatively high concentrations can be tolerated by various cell types [11]. In our experiments, without introducing extraneous elements, a small amount of Nd is ion implanted into the WE43 Mg alloy [12]. The surface composition, morphology, polarization, electrochemical properties, as well as weight loss, pH, and

leached ion concentrations after immersion, are systematically evaluated to determine the corrosion behavior. The cell adhesion and viability are also determined to evaluate the biological response in vitro.

XPS, SEM, AFM, and water contact angle measurements disclose the formation of a smooth and hydrophobic surface layer composed of primarily Nd2O3 and MgO. The Nd ion-implanted sample shows a smaller corrosion current density and higher impedance in both simulated body fluids and cell culture medium. In addition, less weight loss, smaller pH variation, less leaching of magnesium and alloying elements, and much less severe corrosion are observed from the Nd-implanted WE43 magnesium alloy. The enhanced corrosion resistance is ascribed to the stable Nd2O3 layer as well as partially protective MgO inner layer. As shown in Figs. 4 and 5, the cells attach and spread well on the Nd ion-implanted WE43 surface and cells incubated with the extracted medium of the Nd-implanted WE43 for 3 days show viability similar to that observed from the complete cell culture medium, indicating that the Nd ion-implanted WE43 magnesium alloy has good biocompatibility in vitro. Our results supply evidence that Nd self-ion implantation is a promising method to improve both the corrosion resistance and in vitro biocompatibility of the rare-earth WE43 magnesium alloy.

(a)

(b)

Fig. 4. Fluorescent images acquired from the MC3T3-E1 pre-oteoblasts after incubation for 5 hours: (a) Untreated and (b) Nd-implanted WE43 Mg alloy [12].

Fig. 5. In vitro cell viability of MC3T3-E1 pre-oteoblasts cultured in the extraction medium on the untreated and Nd-implanted WE43 for 1 and 3 days [12].

III. POLYMERIC BIOMATERIALS

Dental and orthopedic implants are hard tissue substitutes for impaired human bones in the treatment of trauma, diseases, and aging [13] and polyetheretherketone (PEEK) is a suitable substitute for conventional metallic implants composed of titanium and its alloys [14]. In our experiments, tantalum plasma immersion ion implantation (PIII) is performed to modify the PEEK surface to exploit the favorable properties of PEEK and tantalum. The osteogenic properties of the Ta-PIII modified PEEK are determined systematically using rat bone marrow mesenchymal stem cells (bMSCs) in vitro and the materials are also inserted into rat femur bones for 8 weeks to observe osteo-integration in vivo [15]. After Ta PIII, the elastic modulus, nano-hardness, and elastic recovery are more favorable and in particular, the elastic modulus of the Ta-PIII PEEK sample is closer to that of the human cortical bone than the untreated PEEK. As shown in Figs. 6-9, the Ta-PIII PEEK also exhibits enhanced osteogenic differentiation of rat bMSCs in vitro. In a cortico-cancellous rat femur implantation model, faster and better osteointegration can be observed around the Ta-PIII implants in vivo. Our results reveal the significance of the surface elastic modulus on osteo-integration in vitro and in vivo. The surface-modified PEEK is shown to be more suitable for orthopedic and dental applications and has large clinical potential.

Fig. 6. Characterization of the implants and surrounding bones by micro-CT showing the full and corresponding 2D coronal section views of the rat femur bones with the implants inside: (a and d) PEEK; (b and e) Ta-30; (c and f) Ta-120. Reconstructed 3D models of (g) PEEK, (h) Ta-30 and (i) Ta-120 implants [15].

Fig. 7. Sequential fluorescent labeling: (a) PEEK, (b) Ta-30, and (c) Ta-120. Red, yellow and green represent labeling by alizarin red S, tetracycline hydrochloride and calcein, respectively. (d) Selected area to evaluate the new bone formation process. (e) Histogram showing the percentage of the area of fluorochromes stained bone [**(p<0.01) when compared with PEEK; #(p<0.05) compared with Ta-120] [15].

Fig. 8. Histological observation: The MIA images are shown at low magnification and the insets are shown at high magnification. The images (magnification 40 ×) of the yellow rectangular areas are shown in (a-2) PEEK, (b-2) Ta-30 and (c-2) Ta-120, respectively. The images (magnification 200 ×) of the cyan rectangular areas are shown in (a-3) PEEK, (b-3) Ta-30 and (c-3) Ta-120, respectively. The white arrows mark the direct contact between the implants and new bones and green arrows indicate the fibrous tissue-covering areas [15].

Fig. 9. Histogram of the bone-implant contact based on histomorphometric analysis [***(p<0.001) compared to PEEK; ###(p<0.001) compared to Ta-120] [15].

ACKNOWLEDGMENT

The work was supported by Hong Kong Research Grants Council (RGC) General Research Funds (GRF) Nos. 11301215 and 112212.

REFERENCES

[1] G. Zeb, P. Viel, S. Palacin, and X. T. Le, “On the chemical grafting of

titanium nitride by diazonium chemistry”, RSC Adv., vol. 5, pp. 50298–50305 (2015).

[2] L. J. Zhang, J. J. Fan, Z. Zhang, F .H. Cao, J. Q. Zhang, and C. N. Cao, “Study on the anodic film formation process of AZ91D magnesium alloy”, Electrochim. Acta 52 (2007) pp. 5325–5333 (2007).

[3] H. P. Duan, C. W. Yan, and F. H. Wang, “Growth process of plasma electrolytic oxidation films formed on magnesium alloy AZ91D in silicate solution”, Electrochim. Acta, 52, pp. 5002–5009 (2007).

[4] R. Z. Xu, X. B. Yang, J. Jiang, P. H. Li, X. M. Zhang, G. S. Wu, and P. K. Chu, “Effects of Silver Plasma Immersion Ion Implantation on the Surface Characteristics and Cytocompatibility of Titanium Nitride Films”, Surf. Coat. Technol., vol. 279, pp. 166–170 (2015).

[5] A. Schwabe, U. Meyer, M. Grün, K.D. Voigt, G. Flachowsky, and S. Dänicke. “Effect of rare earth elements (REE) supplementation to diets on the carry-over into different organs and tissues of fattening bulls”, Livest Sci., vol. 143, pp. 5-14 (2012).

[6] M. Zhang, S. L. Ma, K. W. Xu, and P. K. Chu, “Corrosion Resistance of Praseodymium-Ion-Implanted TiN Coatings in Blood and Cytocompatibility with Vascular Endothelial Cells”, Vacuum, vol. 117, pp. 73–80 (2015).

[7] H. Qin, Y. Zhao, Z. An, M. Cheng, Q. Wang, T. Cheng, et al., “Enhanced antibacterial properties, biocompatibility, and corrosion resistance of degradable Mg-Nd-Zn-Zr alloy”, Biomater., vol. 53, pp. 211-220 (2015.

[8] W. J. Wang, X. L. Zhang, G. S. Wu, C. X. Wang, and P. K. Chu, “Praseodymium-Surface-Modified Magnesium Alloy: Retardation of

Corrosion in Artificial Hand Sweat”, Mater. Letts., vol. 163, pp. 85–89 (2016).

[9] T. Zhang, G. Meng, Y. Shao, Z. Cui, and F. Wang, “Corrosion of hot extrusion AZ91 magnesium alloy. Part II: Effect of rare earth element neodymium (Nd) on the corrosion behavior of extruded alloy”, Corros. Sci., vol. 53, pp. 2934-2942 (2011).

[10] H. Hermawan, D. Dube, and D. Mantovani, “Developments in metallic biodegradable stents”, Acta Biomater., vol. 6, pp. 1693-1697 (2010).

[11] F. Feyerabend, J. Fischer, J. Holtz, F. Witte, R. Willumeit, H. Druecker, C. Vogt, and N. Hort, “Evaluation of short-term effects of rare earth and other elements used in magnesium alloys on primary cells and cell lines”, Acta Biomater., vol. 6, pp. 1834-1842 (2010).

[12] W. H. Jin, G. S. Wu, H. Q. Feng, W. H. Wang, X. M. Zhang, and P. K. Chu, “Improvement of Corrosion Resistance and Biocompatibility of Rare-Earth WE43 Magnesium Alloy by Neodymium Self-Ion Implantation”, Corros. Sci., vol. 94, pp. 142 – 155 (2015).

[13] M. Geetha, A. K. Singh, R. Asokamani, and A. K. Gogia, “Ti based biomaterials, the ultimate choice for orthopaedic implants - A review”, Prog Mater Sci., vol. 54, pp. 397-425 (2009).

[14] S. M. Kurtz, J. N. Devine, “PEEK biomaterials in trauma, orthopedic, and spinal implants”, Biomater., vol. 28, pp. 4845-69 (2007).

[15] T. Lu, J. Wen, S. Qian, H. L. Cao, C. Q. Ning, X. X. Pan, X. Q. Jiang, X. Y. Liu, and P. K. Chu, “Enhanced Osteointegration on Tantalum-Implanted Polyetheretherketone Surface with Bone-Like Elastic Modulus”, Biomater., vol. 51, pp. 173 – 183 (2015).

Modification of Biomaterials and Biomedical Devices by Plasma

Immersion Ion Implantation & Deposited and Related Techniques

Paul K Chu*

Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon,

Hong Kong, China

The interactions between biomaterials and living tissues are crucial to clinical success and on

account of increasing clinical demands, biomaterials and biomedical implants are constantly

refined both in sophistication and diversity. Since most biomaterials having the favorable bulk

properties such as durability, strength, hardness, and chemical inertness may not perform the

pre-designed biological functions, surface modification is frequently conducted. Plasma-based

technology offers the unique capability that certain surface properties can be selectively modified

to cater to the biological requirements while desirable bulk properties of the materials such as

those mentioned above can be retained. In particular, plasma immersion ion implantation and

deposition (PIII&D) is widely used in the surface treatment of functional materials and industrial

implants including biomaterials and biomedical implants because it is a non-line-of-sight

technique and especially suitable for biomedical devices with a complex geometry such as

orthopedic implants, bone fixation devices, scoliosis correction rods, cardiovascular stents, and

artificial heart valves. In this invited talk, recent research performed in the Plasma Laboratory of

City University of Hong Kong pertaining to plasma surface treatment of biomaterials and

biomedical devices will be described. Examples include nanostructured coatings/surfaces,

biodegradable metals and polymers, bacteria resistance, and surface biocompatibility.

Keywords: plasma; ion beam; surface modification; biomaterials