author = "Ueda, M{\'a}rio and Souza, G. B. de and Mariano, Samantha de 
                         F{\'a}tima Magalh{\~a}es and Pichon, L.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universidade Estadual de Ponta Grossa} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Institut Pprime - CNRS 
                         -Universite de Poitiers-ENSM}",
                title = "Overcoming sheaths overlapping in a small diameter metallic tube 
                         with one end closed and using a high density plasma from a high 
                         power pulsed hollow cathode discharge",
              journal = "AIP Advances",
                 year = "2018",
               volume = "8",
               number = "1",
                pages = "e085103",
                month = "Aug.",
             abstract = "High voltage sheaths are formed when plasmas are produced by 
                         application of high negative voltage pulses to conductive supports 
                         or components, as in Plasma Immersion Ion Implantation (PIII) 
                         treatments of materials surfaces. For parts with concave shape, as 
                         inside metal tubes, these sheaths behave quite differently 
                         according to the tube configuration and size, as well as, PIII 
                         treatment pressure of operation and pulsing parameters. In this 
                         work, an SS304 tube of 1.1 cm internal diameter and 20 cm length 
                         was pulsed typically at -0.5 to -2.6 kV, 20 Ás pulse length, 500 
                         Hz repetition rate, nitrogen pressure of 5x10-2 mbar and with one 
                         side closed configuration. Different currents (between 10 and 30 
                         A) were used to produce plasmas with sheaths that overlapped or 
                         not, depending on the currents used. To study these sheath 
                         behaviors, a simple plasma diagnostic technique based on a 
                         bi-dimensional mapping of the deposition of sputtered materials 
                         and by etching via the plasma on a Si wafer target surface, both 
                         coming out from the tube, was used. This mapping showed clearly 
                         the border line situation between overlapping and non-overlapping 
                         sheaths in that small tube which allowed to estimate the plasma 
                         density to be around 1011 cm-3 at such a sheath condition, as 
                         previously anticipated by Sheridan. Above that border condition, 
                         nitrogen PIII was successfully obtained in such a small tube of 
                         SS304, producing TiN and Ti2N in samples of Ti6Al4V placed inside 
                         the tube, when temperatures higher than 800\◦C were reached 
                         there. Below the border, no significant uptake of nitrogen was 
                         possible. Using this type of experimental set-up, it is now 
                         possible to explore different hollow cathode behaviors, efficient 
                         or high temperature (above 800\◦C) PIII conditions and also 
                         new utilizations of the plasma ejected from the tube.",
                  doi = "10.1063/1.5040588",
                  url = "http://dx.doi.org/10.1063/1.5040588",
                 issn = "2158-3226",
             language = "en",
           targetfile = "ueda_overcoming.pdf",
        urlaccessdate = "29 nov. 2020"