Rudra, Sukumar

English

Ghent University Academic Bibliography

Grating Light Valves                                              Sukumar RudraSupervisor: Dries Van ThourhoutI. INTRODUCTIONGrating Light Valve1 (GLV) display pixels are  diffraction  gratings,  consisting  of electrostatically  movable  microbeams.  Non-actuated coplanar beams behave like a mirror giving specular reflection. After actuation, the alternate  movable  beams  are  deflected downwards and the grating starts diffracting, which  turns  the  pixel  ON.  GLV  based displays  provides  a  huge  improvement  in contrast, resolution and switching speed over others.  From material perspective, Poly-SiGe has gained serious attention in post processing MEMS  above  CMOS2.  It  has  a  lower deposition  temperature  compared  to  Poly-Si and  possesses  the  necessary  mechanical properties and reliability required for MEMS. The  purpose  of  this  work  is  to  show the functionality  of  poly-SiGe  GLVs.  We  will demonstrate that high resonant frequency and high  contrast  can  be  achieved  for  these devices.II. FABRICATIONA CVD deposited structural SiGe layer was grown with a SiH4: GeH4 flow ratio of 0.9:1 and a  B2H6 flow over varying thickness at a chuck temperature of 460°C. Extra layers of 5 nm  SiC  and  30  nm  AlCu  were  added  by sputtering on top of the SiGe to increase the reflectivity of the structure.III. RESULTS The response of the GLVs to a DC voltage is shown in Fig. 1.  A clear change in intensity of the 1st order diffracted light with increasing actuation voltage can be observed.Laser  Doppler  Vibrometry  was  used  to determine the dynamic response of the GLVs. The underdamped nature of a single actuated microbeam is  shown  in  Fig  2.  A resonance frequency of 1.67 MHz was found. It can be seen  that  the  settling  time  increases  to  5us because of insufficient damping.Fig 1. DC response of a GLV device.Fig 2. Underdamped behavior of GLVs.IV. CONCLUSIONSWe demonstrated the operation of a poly-SiGe based GLV with a high contrast of 300:1 and a resonant frequency of 1.67 MHz.V. REFERENCES[1]  Trisnadi  et  al,  Photonics  West  2004, Micromachining  and  Microfabrication Symposium, 5348-05[2]  A.  Witvrouw,  Scripta  Materialia,  59 (2008), 945-949.

Grating light valves

https://biblio.ugent.be/publication/1155725/file/1155727.pdf

Grating light valves

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Ghent University Academic Bibliography