Titel Deelnemers "Korte inhoud" "Improved Field Electron Emission Properties of Phosphorus and Nitrogen Co-Doped Nanocrystalline Diamond Films" "Fernando LLORET, Sankaran KAMATCHI JOTHIRAMALINGAM, Josue Millan-Barba, Derese DESTA, Rozita ROUZBAHANI BAYATANI, Paulius POBEDINSKAS, Marina Gutierrez, Hans-Gerd BOYEN, Ken HAENEN" "Nanocrystalline diamond (NCD) field emitters have attracted significant interest for vacuum microelectronics applications. This work presents an approach to enhance the field electron emission (FEE) properties of NCD films by co-doping phosphorus (P) and nitrogen (N) using microwave plasma-enhanced chemical vapor deposition. While the methane (CH4) and P concentrations are kept constant, the N(2)concentration is varied from 0.2% to 2% and supplemented by H-2. The composition of the gas mixture is tracked in situ by optical emission spectroscopy. Scanning electron microscopy, atomic force microscopy (AFM), transmission electron microscopy, and Raman spectroscopy are used to provide evidence of the changes in crystal morphology, surface roughness, microstructure, and crystalline quality of the different NCD samples. The FEE results display that the 2% N(2)concentration sample had the best FEE properties, viz. the lowest turn-on field value of 14.3 V/mu m and the highest current value of 2.7 mu A at an applied field of 73.0 V/mu m. Conductive AFM studies reveal that the 2% N(2)concentration NCD sample showed more emission sites, both from the diamond grains and the grain boundaries surrounding them. While phosphorus doping increased the electrical conductivity of the diamond grains, the incorporation of N(2)during growth facilitated the formation of nano-graphitic grain boundary phases that provide conducting pathways for the electrons, thereby improving the FEE properties for the 2% N(2)concentrated NCD films." "Highly Conductive Diamond-Graphite Nanohybrid Films with Enhanced Electron Field Emission and Microplasma Illumination Properties" "Adhimoorthy Saravanan, Bohr-Ran Huang, Sankaran KAMATCHI JOTHIRAMALINGAM, Nyan-Hwa Tai, I-Nan Lin" "Bias-enhanced nucleation and growth of diamond-graphite nanohybrid (DGH) films on silicon substrates by microwave plasma enhanced chemical vapor deposition using CH4/N-2 gas mixture is reported herein. It is observed that by controlling the growth time, the microstructure of the DGH films and, thus, the electrical conductivity and the electron field emission (EFE) properties of the films can be manipulated. The films grown for 30 min (DGHB30) possess needle-like geometry, which comprised of a diamond core encased in a sheath of sp(2)-bonded graphitic phase. These films achieved high conductivity of sigma = 900 S/cm and superior EFE properties, namely, low turn-on field of 2.9 V/mu m and high EFE current density of 3.8 mA/cm(2) at an applied field of 6.0 V/mu m. On increasing the growth time to 60 min (the DGH(B60)), the acicular grain growth ceased and formed nanographite clusters or defective diamond clusters (n-diamond). Even though DGH(B60) films possess higher electrical conductivity (s = 1549 S/cm) than the DGHB30 films, the EFE properties degraded. The implication of this result is that higher conductivity by itself does not guarantee better EFE properties. The nanosized diamond grains with needle-like geometry are the most promising ones for the electron emission, exclusively when they are encased in graphene-like layers. The salient feature of such materials with unique granular structure is that their conductivity and EFE properties can be tuned in a wide range, which makes them especially useful in practical applications." "Local probing of the enhanced field electron emission of vertically aligned nitrogen-doped diamond nanorods and their plasma illumination properties" "S. Deshmukh, Sankaran KAMATCHI JOTHIRAMALINGAM, K. Srinivasu, S. Korneychuk, D. Banerjee, A. Barman, G. Bhattacharya, D. M. Phase, M. Gupta, J. Verbeeck, K. C. Leou, I. N. Lin, Ken HAENEN, Susanta S. Roy" "A detailed conductive atomic force microscopic investigation is carried out to directly image the electron emission behavior for nitrogen-doped diamond nanorods (N-DNRs). Localized emission measurements illustrate uniform distribution of high-density electron emission sites from N-DNRs. Emission sites coupled to nano graphitic phases at the grain boundaries facilitate electron transport and thereby enhance field electron emission from N-DNRs, resulting in a device operation at low turn-on fields of 6.23 V/mu m, a high current density of 1.94 mA/cm(2) (at an applied field of 11.8 V/mu m) and a large field enhancement factor of 3320 with a long lifetime stability of 980 min. Moreover, using N-DNRs as cathodes, a microplasma device that can ignite a plasma at a low threshold field of 390 V/mm achieving a high plasma illumination current density of 3.95 mA/cm2 at an applied voltage of 550 V and a plasma life-time stability for a duration of 433 min was demonstrated." "Low Temperature Synthesis of Lithium-Doped Nanocrystalline Diamond Films with Enhanced Field Electron Emission Properties" "Sankaran KAMATCHI JOTHIRAMALINGAM, Kalpataru Panda, Ping-Yen Hsieh, Paulius POBEDINSKAS, Jeong Young Park, Marlies VAN BAEL, Nyan-Hwa Tai, I-Nan Lin, Ken HAENEN" "Low temperature (350 degrees C) grown conductive nanocrystalline diamond (NCD) films were realized by lithium diffusion from Cr-coated lithium niobate substrates (Cr /LNO). The NCD/Cr/LNO films showed a low resistivity of 0.01 Omega.cm and excellent field electron emission characteristics, viz. a low turn-on field of 2.3 V/mu m, a high-current density of 11.0 mA/cm(2) (at 4.9 V/m), a large field enhancement factor of 1670, and a life-time stability of 445 min (at 3.0 mA/cm(2)). The low temperature deposition process combined with the excellent electrical characteristics offers a new prospective for applications based on temperature sensitive materials." "Engineering the interface characteristics on the enhancement of field electron emission properties of vertically aligned hexagonal boron nitride nanowalls" "Sankaran KAMATCHI JOTHIRAMALINGAM, Quang HOANG, K. Srinivasu, S. Korneychuk, Stuart TURNER, Sien DRIJKONINGEN, Paulius POBEDINSKAS, J. Verbeeck, K. C. Leou, I. N. Lin, Ken HAENEN" "Utilization of Au and nanocrystalline diamond (NCD) as interlayers noticeably modifies the microstructure and field electron emission (FEE) properties of hexagonal boron nitride nanowalls (hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3V mu m(-1), attaining FEE current density of 2.58mAcm(-2) and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride (aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability." "Stable Field Electron Emission and Plasma Illumination from Boron and Nitrogen Co‐Doped Edge‐Rich Diamond‐Enhanced Carbon Nanowalls" "Mateusz Ficek, Bartlomiej Dec, Kamatchi Jothiramalingam Sankaran, Krzysztof Gajewski, Piotr Tatarczak, Igor Wlasny, Andrzej Wysmolek, Ken HAENEN, Teodor Gotszalk, Robert Bogdanowicz" "Superior field electron emission (FEE) characteristics are achieved in edge-rich diamond-enhanced carbon nanowalls (D-ECNWs) grown in a single-step chemical vapor deposition process co-doped with boron and nitrogen. The structure consists of sharp, highly conductive graphene edges supplied by a solid, diamond-rich bottom. The Raman and transmission electron microscopy studies reveal a hybrid nature of sp(3)-diamond and sp(2)-graphene in these nanowalls. The ab-initio calculations were carried out to support the experimental observations of diamond-graphene hybrid structure. Finally, this hybrid D-ECNWs is employed as a cathode in an FEE device resulting in a low turn-on field of 3.1 V mu m(-1), a large field enhancement factor, a high FEE J(e) of 2.6 mA cm(-2), and long lifetime stability of 438 min. Such an enhancement in the FEE originates from the unique materials combination, resulting in good electron transport from the graphene phases and efficient FEE of electrons from the sharp edges on the nanowalls. The prospective application of these materials is displayed by employing these hybrids as cathodes in a microplasma device ensuing a low threshold voltage of 160 V and high plasma stability of 140 min, which confirms the role of these hybrid structured nanowalls in the enhancement of electron emission." "Nitrogen Incorporated (Ultra)Nanocrystalline Diamond Films for Field Electron Emission Applications" "Sankaran KAMATCHI JOTHIRAMALINGAM, Ken HAENEN" "Diamond is eminent to own a series of outstanding physical and chemical properties, thus rendering it to be a strong cold cathode material for field electron emission (FEE) applications. FEE from diamond materials comprises the supply of electrons to the conduction band of the materials, transport through bulk, and lastly emission at the surface. In this chapter, the enhancement in the FEE characteristics of nitrogen incorporated (ultra)nanocrystalline diamond ((U)NCD) films and their related nanostructures is discussed. Ion implantation, in-situ impurity doping in plasma, and post plasma treatment processes have been employed to incorporate nitrogen in (U)NCD. The possible mechanism through which the change in microstructure enhances the FEE characteristics of nitrogen incorporated (U)NCD films/nanostructures is discussed." "Improvement on electrical conductivity and electron field emission properties of Au-ion implanted ultrananocrystalline diamond films by using Au-Si eutectic substrates" "Sankaran KAMATCHI JOTHIRAMALINGAM, B. Sundaravel, N. H. Tai, I. N. Lin" "In the present work, Au-Si eutectic layer was used to enhance the electrical conductivity/electron field emission (EFE) properties of Au-ion implanted ultrananocrystalline diamond (Au-UNCD) films grown on Si substrates. The electrical conductivity was improved to a value of 230 (Omega cm)(-1), and the EFE properties was enhanced reporting a low turn-on field of 2.1 V/mu m with high EFE current density of 5.3 mA/cm(2) (at an applied field of 4.9 V/mu m) for the Au-UNCD films. The formation of SiC phase circumvents the formation of amorphous carbon prior to the nucleation of diamond on Si substrates. Consequently, the electron transport efficiency of the UNCD-to-Si interface increases, thereby improving the conductivity as well as the EFE properties. Moreover, the salient feature of these processes is that the sputtering deposition of Au-coating for preparing the Au-Si interlayer, the microwave plasma enhanced chemical vapor deposition process for growing the UNCD films, and the Au-ion implantation process for inducing the nanographitic phases are standard thin film preparation techniques, which are simple, robust, and easily scalable. The availability of these highly conducting UNCD films with superior EFE characteristics may open up a pathway for the development of high-definition flat panel displays and plasma devices. (C) 2015 AIP Publishing LLC." "Field electron emission enhancement in lithium implanted and annealed nitrogen-incorporated nanocrystalline diamond films" "Sankaran KAMATCHI JOTHIRAMALINGAM, K. Srinivasu, C. J. Yeh, J. P. Thomas, Sien DRIJKONINGEN, Paulius POBEDINSKAS, B. Sundaravel, K. C. Leou, K. T. Leung, Marlies VAN BAEL, M. Schreck, I. N. Lin, Ken HAENEN" "The field electron emission (FEE) properties of nitrogen-incorporated nanocrystalline diamond films were enhanced due to Li-ion implantation/annealing processes. Li-ion implantation mainly induced the formation of electron trap centers inside diamond grains, whereas post-annealing healed the defects and converted the a-C phase into nanographite, forming conduction channels for effective transport of electrons. This resulted in a high electrical conductivity of 11.0 S/cm and enhanced FEE performance with a low turn-on field of 10.6 V/mu m, a high current density of 25.5 mA/cm(2) (at 23.2 V/mu m), and a high lifetime stability of 1,090 min for nitrogen incorporated nanocrystalline diamond films. Published by AIP Publishing." "Microstructural Effect on the Enhancement of Field Electron Emission Properties of Nanocrystalline Diamond Films by Li-Ion Implantation and Annealing Processes" "Sankaran KAMATCHI JOTHIRAMALINGAM, Chien-Jui Yeh, Srinivasu Kunuku, Joseph Palathinkal Thomas, Paulius POBEDINSKAS, Sien DRIJKONINGEN, Balakrishnan Sundaravel, Keh-Chyang Leou, Kam Tong Leung, Marlies VAN BAEL, Matthias Schreck, I-Nan Lin, Ken HAENEN" "The impact of lithium-ion implantation and postannealing processes on improving the electrical conductivity and field electron emission (FEE) characteristics of nitrogen-doped nanocrystalline diamond (nNCD) films was observed to be distinctly different from those of undoped NCD (uNCD) films. A high-dose Li-ion implantation induced the formation of electron trap centers inside the diamond grains and amorphous carbon (a-C) phases in grain boundaries for both types of NCD films. Postannealing at 1000 C healed the defects, eliminated the electron trap centers, and converted the a-C into nanographitic phases. The abundant nanographitic phases in the grain boundaries of the nNCD films as compared to the uNCD films made an interconnected path for effectual electron transport and consequently enhanced the FEE characteristics of nNCD films."