This paper demonstrates a 3D microlithography system where an array of 5 mm Ultra Violet-Light Emitting Diode (UV-LED) acts as a light source. The unit of the light source is a UV-LED, which comes with a length of about 8.9 mm and a diameter of 5 mm. The whole light source comprises 20 × 20 matrix of such 5 mm UV-LEDs giving a total number of 400 LEDs which makes it a very favorable source with a large area for having a batch production of the desired microstructures. This light source is able to give a level of precision in microfabrication which cannot be obtained using commercial 3D printers. The whole light source performs continuous rotational movement once it is turned on. This can also move up and down in a vertical direction. This multidirectional light source also comprises a multidirectional sample holder. The light source teaming up with the multidirectional sample holder highly facilitates the process of fabrication of a huge range of 3D structures. This article also describes the different levels of characterization of the system and demonstrates several fabricated 3D microstructures including high aspect ratio vertical micro towers, twisted turbine structures, triangles, inclined pillar ‘V’ structures, and hollow horn structures as well.
A novel pretreatment enhancing diamond nucleation has been developed for diamond growth over a large area using a magnetoactive microwave plasma chemical vapor deposition method. After the predeposition of carbon films on Si(100) substrates using CH4/CO2/He gas mixtures, diamond films with high nucleation densities were obtained after a subsequent 2 h growth process commonly employed using a CH4/CO2/H2 gas mixture. In the present study, especially, the effect of CO2 concentration in the CH4/CO2/He gas mixture in the pretreatment process has been examined on the carbon film growth. The results show that the diamond nucleation with densities as high as ∼109/cm2 was attained for small CO2 concentrations of 1%–2% during the pretreatment process, while no successful enhancement was enabled for Si substrates pretreated at high CO2 concentrations beyond 3.7%. The structural property of the predeposited carbon films significantly influenced the diamond nucleation. This was evidenced by in situ data of optical emission spectroscopy and quadrupole mass spectroscopy during the pretreatment process, as well as by ex situ data of morphology and composition of the specimens. The volume density of the carbon films obtained after the pretreatment was maximized at a CO2 concentration of 1.9%. The bonding nature of the carbon atoms deduced from the related Raman scattering spectra apparently changed with CO2 concentration. The role of the predeposited carbon films is discussed in relation to etching and agglomeration phenomena during the subsequent diamond growth process.
Nucleation-enhanced pretreatments have been studied for large-area diamond growth on Si
(100) substrates using magneto-active microwave plasma chemical vapor deposition (CVD) at
low pressures below 10 Pa. In this study, an optimal CO2 composition in the CH4/He plasma used
for the pretreatment was mainly examined for the case of a low substrate temperature of ∼600°C.
A two-hour subsequent growth using a CH4[5 sccm]/CO2[10 sccm]/H2[85 sccm] gas mixture after
the pretreatment resulted in <100>-oriented growth of diamond Particles with a high density (∼109/cm2) on Si substrates pretreated at CO2 concentrations of 1–2%. On the other hand, at CO2
concentrations higher than these, the carbon films deposited during the pretreatment were less
dense and were almost completely etched off after a 10-min treatment using the growth plasma. It
was found that quadrupole mass spectra, optical emission spectra and Raman scattering spectra
changed substantially when CO2 beyond 3.8% was added to the source gas.
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