Silicon nitride membranes

Figure 2.37 Temperature profiles across the membrane covering the reaction channel of the T micro reactor for a silicon and a silicon nitride membrane and two different heater designs, as discussed by Quiram et al. [128].

The next step was the introduction of ion implantation to dope Si for thermometers. Downey et al. [66] used micromachining to realize a Si bolometer with an implanted thermometer. This bolometer had very little low-frequency noise. The use of thermometers doped by neutron transmutation instead of melt doping is described by Lange et al. [67], The evolution of bolometers sees the replacement of the nylon wires to make the conductance to the bath, used by Lange et al. with a micromachined silicon nitride membrane with a definite reduction in the heat capacity associated to the conductance G [68],... 

Fig. 7 Schematics of a nanometer scale M-A-M diode (not drawn to scale in relative thickness). Top schematic is the cross section of a silicon wafer with a nanometer scale pore etched through a suspended silicon nitride membrane. Middle and bottom schematics show a Au/SAM/Au junction formed in the pore area. (Reprinted with permission from [30])...

Nanopore junctions, shown in Fig. 10.10, were investigated by Reed and coworkers [43-45, 71]. A small hole, 30-50 nm in diameter, was etched in a silicon nitride membrane by e-beam lithography. One side of the hole was filled with evaporated gold and a SAM (consisting of —1000 molecules) was formed inside the hole when placed in a solution. A second Au electrode was then deposited on the other side of the hole by evaporation. 

Figure 3.48 Exploded schematic view of a flow-cell FPW liquid sensor. The silicon chip containing die thin silicon-nitride membrane, piezoelectric film and transducers is sandwiched between two etched silicon chips. The upper chip is a cap with fluid inlet and outlet fittings, b also provides vias for contact to a temperature-sensing polysilicon resistor deposited on the FPW chip below it. The lower chip introduces transducer contact leads and protects the underside of the membrane fitm contact with the fluid. (Hgwc courtesy of Beo Costello, Bokeley Microliulratitents, Inc.)...

Fig. 10.25 (a) PPy chemo-resistor fabricated on a silicon nitride membrane,... 

Ma SH, Lepak LA, Hussain RJ, Shain W, Shuler ML. An endothelial and astrocyte co-culture model of the blood-brain barrier utilizing an ultra-thin, nanofabricated silicon nitride membrane. Lab Chip 2005 5 74-85. 

The results provided in the 1st PT campaign for pH, conductivity, Ca, K, Na and chloride were obtained by in-house fabricated microelectrodes (Chapter 4.1.4 of this book). The sensor used for pH determination is a pH-ISFET with silicone nitride membrane, the sensors for Na+, K+, Ca2+ and Cl- are ISFETs with ion-selective membranes, while the sensors for conductivity is a 4-bar platinum electrode. All the circuits used for measuring with the sensors (ISFET meter and conductivity meter) were also developed in-house. The results for the ions (Na+, K+, Ca2+ and Cl-) were received being expressed in activity, therefore could not be compared with the other PT results. 

Tiggelaar et al. [263] deposited a 150-nm-thick layer of silicon-rich silicon nitride on a microstructured silicon surface by low-pressure CVD by using SiH2Cl2 and NH3 gases. The silicon nitride membrane was part of a high-temperature microreactor with integrated heater and sensor patterns. 

Figure 5.58 (a) TEM image of a nanoparticle monolayer printed onto a silicon nitride membrane window (b) TEM image of a bilayer printed onto a silicon nitride membrane ... 

New, alternative methods for membrane preparation are also reported in the literature. For example, the membrane microsieves with a very regular pore structure (pores from several micrometers down to 0.1-0.2 pm) are prepared via photolithography [101,102]. These very thin silicon nitride membranes combine a very high porosity with extremely high permeabilities, much larger than the track-etched or other microfiltration membranes with similar pore size. 

Rubinsky s group presented the first microfluidic device to electroporate a cell (Davalos et al., 2000 Huang and Rubinsky, 1999). Their devices consisted of three silicon chips bonded together to form two chambers, separated by a 1 pm thick silicon nitride membrane with a 2—10 pm diameter hole. Because silicon nitride is nonconductive, any electrical current flowing from the top chamber to the bottom chamber must pass through this microhole. A cell suspension was introduced into the top chamber, followed by the immobilization of one cell in the hole by lowering the pressure in the bottom chamber. 

Harris, S. and Shuler, M.L. (2003). Growth of endothelial cells on microfabricated silicon nitride membranes for an in vitro model of the blood-brain barrier. Biotechnol. Bioprocess Eng. 8 246. 

Accordingly, the nitroaniline OPE was tested in the nanopore, in the absence of an orthogonal external electric field, to determine its electronic characteristics. A series of control experiments were first performed with alkanethiol-derived SAMs and systems containing no molecules. Both the Au-alkanethiolate-Au junctions and the Au-silicon nitride membrane-Au junctions showed current levels at the noise limit of the apparatus (< 1 pA) for both bias polarities at both room and low temperatures. The Au-Au junctions gave... 

They were also found to be more significant in long channels, at least for cylindrical pores in silicon nitride membranes. 

The two chambers containing the electrolyte solution separated by the silicon-nitride membrane form a capacitor (C in Fig. 11b) of about... 

Silicon nitride is a good insulator and acts as barrier against all kinds of diffusion to water and ions. Due to thermal insulation properties, heater structures are suspended on silicon nitride membrane or fixtures. Its ultrastrong resistance to oxidation and many etchants makes it a superior material for masks in deep etching. It is also used as high-strength electrical insulator. 

Zhu J, Barrow D. 2005. Analysis of droplet size during crossflow membrane emulsification using stationary and vibrating micromachined silicon nitride membranes. / Membr Sci 261 136-144. 

The earliest work on imaging block copolymer microdomains relied heavily upon transmission electron microscopy (TEM), and it still proves to be a useful tool to this day [19]. Samples are either microtomed or solvent cast to produce thin (ca. 100 nm) sections. PS-PI or PS-PB samples can be stained with osmium tetroxide to increase contrast. Osmium tetroxide reacts selectively with unsaturated double bonds such as found in PI or PB microdomains so as to provide mass contrast [21]. Unfortunately, TEM requires that the samples be freestanding or transferred to a transparent support (e.g. carbon), a cumbersome and time-consuming process that is largely incompatible with silicon or GaAs wafers. While silicon nitride membranes can be employed for TEM, these expensive and delicate structures are not easily accessible to all researchers [22]. 

The response of BCP microdomains to an applied electric field was elegantly demonstrated when a thin film of PS-b-PMMA was placed between two gold electrodes on a silicon nitride membrane or window. The silicon nitride is transparent to electrons and the electron density difference between PS and PMMA is sufficient to be distinguishable with TEM. When a film is annealed without an E field, the cylinder orientation is random (Figure 10(a)). Such films contain a large number of defeas as well as highly curved cylindrical domains. The orientation of the cylinders is not influenced by... 

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