Nucleation and growth of MW-PECVD diamond layers on various substrates Ph.D. Thesis book Hajnalka K. Csorbai Consultant: Dr. Hárs György Dr. Kálmán Erika 2007
Antecedents: Diamond - apart from its beauty possess many special physical and chemical properties which may make it very important material for future industries. E.g. it is a very good electric insulator, while at the same time it is also a very good heat conductor (a rare combination) and has very low permittivity. The possibility of the utilization of these arose since the emergence of the low pressure growth techniques in the eighties and research is still ongoing in this direction in several leading industrial countries. The preparation of artificial diamond by Low Pressure Chemical Deposition (LPCVD) gives rise of many yet unresolved problems whose solution presents great challenges to all researchers on the field of material sciences. Although various diamond thin layers are prepared at the present technological level on different substrates but the theory of the layer formation is not yet clear. With the progress of our theoretical understanding trial and error growth experiments could be replaced by much more effective purposeful developments. Goals: The goal of my thesis work was the preparation of contiguous diamond layers applicable for corrosive protective coating. The first problem I had to solve was the creation of pinhole free diamond layers. This I achieved by modifying the sample heating and electric bias in a Microwave Plasma Enhanced Chemical Vapor Deposition (MEW- PECVD) device. For practical applications we need a method to prepare diamond coated 3D structured surfaces. For this purpose I developed a selective diamond deposition technique. A further requirement of contacting diamond and metal layers arose from the possibility to use diamond in semiconductor devices. I. realized this by coating various metal surfaces with diamond. A problem for some applications if the coating is not elastic enough so I aimed at the preparation of thinner contiguous diamond coating. I researched the nucleation and growth of diamond layers from CH 4 /H 2 gas mixtures on Si, SiN x, SiON surfaces and on Si/SiO 2 structure in an MW-PWCVD device.
Experimental: I examined the coatings with various techniques: laser interferometry, anisotropic chemical etching, scanning electron microscope (SEM), atomic force microscopy (AFM) and RAMAN spectroscopy. New scientific achievements: 1. Preparation of contiguous corrosive resistant diamond layer on planar Si monocrystal surface.. [1], [2], [5], [6], [7], [8], [10], [13] I prepared pinhole free diamond coatings on planar Si surfaces by optimizing the nucleation and growth times and parameters. I found the optimal nucleation and growth times to be 12 mins and 8 hours with optimal temperatures of 850 C and 850 C respectively. 2. Preparation of contiguous diamond layer on 3D structured monocrystalline Si surface. [1], [2], [5], [6], [8], [9], [11], [14] I developed the method of electric bias feedback which made the coating of non-planar surfaces possible by using computer simulation to study the electric potential on 3D structured surfaces. 3. Selective diamond deposition on Si/SiO 2 structure, preparation of a diamond layered flow meter structure. [3], [4], [5], [6], [12], [15], [16], [17] 3.1 I performed selective diamond deposition on Si/SiO 2 structure for corrosive protection coating and proposed a possible application of this method for flow meter sensor structures 3.2 With this selective diamond deposition technique I created a self-supporting direction sensitive flow meter structure from diamond. 4. Preparation of a combined Diamond/DLC protective coating. 3], [4], [16], [17], [18], [20] 4.1 I determined that the optimal layer thickness for such coatings is 150 nm.
4.2 I found that this combined Diamond/DLC layer was much more resistant against a KOH/i-propil compound then independently prepared Diamond and DLC layers of the same thicknesses used in this coating combined or single Diamond or DLC layers of the combined layer thickness would be. Further studies: Many different unresolved problem limits the applicability of diamond layers. A widely researched area is the doping and contacting diamond layers. In 2004 the Chemical research Institute of the Hungarian Academy of Sciences acquired a microwave activated plasma enhanced chemical vapor deposition (MW-PECVD) instrument capable of boron doping of diamond layers. I am using this device to study the possibilities of boron doping. The area of applicability is further enhanced by creating diamond layers on Cu, Ni and Ir surfaces which I am still researching.. Other carbon layers and the combination of those beside of diamond ones present great possibilities for further research. These layers may also be prepared with the same instrument. I will try to create carbon nanotubes and DLC layers in the future. References related to my theses: 1. H.K.Csorbai, A. Kováts, Sz. Kátai, Gy. Hárs, Cs. Dücső, E. Kálmán, P. Deák: Microwave-CVD Diamond layers on 3D structured Si for Protective Coating, Diamond and Related Materials 11, Vol. 3-6, p. 519-522, 2002 2. H.K.Csorbai, P. Fürjes, Gy. Hárs, Cs. Dücső, I. Bársony, E. Kálmán, P. Deák: Microwave-CVD Diamond Protective Coating for 3D structured Silicon Microsensors, Material Science Forum, Vol. 414-415, p. 69-73, 2003 3. H.K.Csorbai, G. Kovách, G. Pető, P. Csíkvári, A. Karacs and E. Kálmán: Combination of CVD diamond and DLC film growth with pulsed laser deposition to enhance the corrosive protection of diamond layers, Material Science Forum, Vol. 473-474, p. 67-72, 2005
4. H.K.Csorbai, G. Kovách, P. Fürjes, P. Csíkvári, A. Sólyom, Gy. Hárs and E. Kálmán: Development of self-supporting polycrystalline diamond bridge, Material Science Forum, Vols. 537-538 (2007) pp. 145-150, közlésre elfogadva, 2007 5. H.K.Csorbai, G. Kovách, G. Pető, P. Csíkvári, A. Karacs, Gy. Hárs and E. Kálmán: Diamond/DLC double layer used in corrosive protective coating, Applied Surface Science, elfogadva 6. Csorbai H, Hárs Gy., Dücső Cs., Bársony I., Kálmán E. és Deák P.: Korrózióvédő gyémántrétegek előállítása nyomásmérő szenzorokon való alkalmazás céljából, Technika folyóirat, 2002 7. Kováts A., Csorbai H., Deák P.: Mikrohullámú CVD módszerrel előállított gyémántrétegek alkalmazási lehetőségei, KOHÁSZAT Bányászati és Kohászati Lapok, 2002 Oral presentations: 8. H. Csorbai, A. Kováts, Sz. Kátai, Gy. Hárs, Cs. Dücsõ, E. Kálmán, P. Deák Corrosion protective diamond layer on flat Si surface, XI th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, Porto, Portugália, 2000 9. H. Csorbai, A. Kováts, Sz. Kátai, Gy. Hárs, Cs. Dücső, P. Deák and E. Kálmán: MW-PECVD diamond layers on 3D structured Si for Protective Coating ISE Conference, San Francisco, USA, 2001 10. H. Csorbai, A. Kováts, Sz. Kátai, Gy. Hárs, Cs. Dücső, E. Kálmán, P. Deák: Microwave-CVD Diamond layers on 3D structured Si for Protective Coating, XII th Europian Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, Budapest, 2001 11. H. Csorbai: Korrózióálló gyémántréteg előállítása, Kémiai Doktori Iskola, 2000 12. H. Csorbai: Gyémántréteg kialakítása strukturált Si felületen, Kémiai Doktori Iskola, 2001 13. H.K. Csorbai: Gyémántrétegek alkalmazásának legújabb lehetőségei, Kémiai Doktori Iskola, 2002 14. Gy. Hárs, H. Csorbai, P. Deák: Tűlyukmentes gyémántréteg előállítása MW- PECVD módszerrel II. Országos Anyagtudományi, Anyagvizsgálati és Anyaginformatikai Konferencia és Kiállítás, Balatonfüred, 1999
15. H. Csorbai, P. Fürjes, Gy. Hárs, Cs. Dücső, I. Bársony, E. Kálmán, P. Deák: Microwave-CVD Diamond Protective Coating for 3D structured Silicon Microsensors III. Országos Anyagtudományi, Anyagvizsgálati és Anyaginformatikai Konferencia és Kiállítás, Balatonfüred, 2001 16. H.K. Csorbai: Legújabb eredményeink CVD módszerrel történő gyémántleválasztás terén, PhD hallgatók II. Anyagtudományi napja, Veszprém, 2002 17. H.K.Csorbai, G. Kovách, G. Pető, P. Csíkvári, A. Karacs and E. Kálmán: Combination of CVD diamond and DLC film growth with pulsed laser deposition to enhance the corrosive protection of diamond layers, IV. Országos Anyagtudományi, Anyagvizsgálati és Anyaginformatikai Konferencia és Kiállítás, Balatonfüred, 2003 18. H.K. Csorbai, G. Kovách, Gy. Hárs, E. Kálmán: Legújabb eredményeink CVD módszerrel történő gyémántleválasztás terén ELFT Fizikus Vándorgyűlés, Szombathely, 2004 19. H.K. Csorbai, G. Kovách, P. Fürjes, P. Csíkvári, A. Sólyom, Gy. Hárs and E. Kálmán: Newest results on the field of CVD diamond deposition, V. Országos Anyagtudományi, Anyagvizsgálati és Anyaginformatikai Konferencia és Kiállítás, Balatonfüred, 2005 Patent applications: 20. Dr. Pető Gábor, Kováchné Csorbai Hajnalka, Karacs Albert, Kovách Gergely, Dr. Kálmán Erika, Dr. Deák Péter, Dr. Molnár György, Dr. Hárs György: Korrózív kémiai közegben ellenálló gyémánt- gyémántszerű szén védőrétegrendszer és előállítása, 2004.07.27, 0425399 iktatási szám, P0401509 ügyszám, MTA MFA-MTA KK- BME Other scientific papers 21. G. Kovách, H.K. Csorbai, Gy.Z. Radnóczi, Gy. Vida, Z. Pászti, G. Pető and A. Karacs: Properties of laser ablated amorphous carbon layer, Material Science Forum, Vol. 414-415, p. 127-132, 2003 22. E. Kálmán, P. Nagy, Á. Csanády, K. Papp, H. K. Csorbai, Cs. Hunyadi, J. Telegdi: AFM and SEM: competing or complementary techniques? Material Science Forum, Vol. 414-415, p. 241-251, 2003
23. G. Kovách, H.K. Csorbai, G. Dobos, A. Karacs and G. Pető: Formation and characterization of electric contacts on CVD diamond films prepared by ion implantation, Material Science Forum, 2005 24. G. Kovách, H.K.Csorbai, Gy.Z. Radnóczi, Gy. Vida, Z. Pászti, G. Pető and A. Karacs: Properties of laser ablated amorphous carbon layer, EMCR Conference, Strassbourg, Franciaország, 2001 25. G. Kovách, G. Pető, A. Karacs, M. Veres, H.K. Csorbai, A. Sólyom: Thin film carbon layers with continously changing bounding properties, Material Science Forum, Vol. 537-538 p. 207-214, nyomtatás alatt, 2007 26. G. Kovách, G. Pető, A. Karacs, Gy. Radnoczi H.K. Csorbai, L. Guczi, M. Veres, M Koos, L. Papadimitriou: Electronic and structural properties of Ar + ion bombarded diamond, elbírálás alatt
Acknowledgements: I am obliged to my consultants Dr György Hárs and Dr. Erika Kálmán for their help in my PhD work. I thank Dr Gábor Pálinkás, Dr. Péter Richter, Dr. Péter Deák and Dr. László Kocsányi for providing funding and infrastructure for my research, Dr. András Sólyom, Dr. Csaba Dücső, Dr. Gábor Pető, Gergely Kovách, Katalin Papp, Dr. Mária Deákné Tóth, Andrásné Csanády Dr. and Dr. László Nemes for their help with my experiments and their many advice. I am also grateful to the whole staff of the Department of Surface Modification and Nanostructures of the Chemical Research Center and the Surface Science Laboratory of Budapest University of Technology and Economics for I could rely on them any time I needed any kind of help.