Si wafers uniformly spaced; bonding and diagnostics

Rhee, Ilsu; Gasparini, Francis M.; Petrou, A.; Bishop, David J.

doi:10.1063/1.1141166

Cited by 34 publications

(20 citation statements)

References 12 publications

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“…These two wafers are bonded together using direct wafer bonding [10,11]. This improves our earlier protocol [12], and is much more reliable. Diagnostics of the bonding quality include infrared (IR) imaging and IR interference experiments [11,12].…”

Section: Sarabjit Mehta and Francis M Gasparinimentioning

confidence: 93%

Specific Heat and Scaling of4HeConfined in a Planar Geometry

Mehta

Gasparini

1997

Phys. Rev. Lett.

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We report measurements of the specific heat of thick helium films to test scaling predictions near the superfluid transition, T l . These films, bounded by two silicon wafers, range in thickness from 0.107 to 0.692 mm. The specific heat of the films is suppressed relative to that of bulk helium, and the difference of the data from bulk helium scales well with the exponent of the correlation length. We propose an empirical scaling function which fits the data well for T . T l , and yields the surface specific heat. We also compare the data with various theoretical calculations and experiments. We find that the calculations underestimate the effect of confinement. [S0031-9007(97)

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Section: Sarabjit Mehta and Francis M Gasparinimentioning

confidence: 93%

Specific Heat and Scaling of4HeConfined in a Planar Geometry

Mehta

Gasparini

1997

Phys. Rev. Lett.

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“…Faced with these requirements, a decision to move away from the use of Si-SiO 2 bonding as described by Rhee et al 9 was taken. This was based on anecdotal information about the strength of the Si-SiO 2 bond and the requirement to avoid numerous supporting posts.…”

Section: Introductionmentioning

confidence: 99%

Anodically bonded submicron microfluidic chambers

Dimov

Bennett

Córcoles

et al. 2010

Review of Scientific Instruments

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We demonstrate the use of anodic bonding to fabricate cells with characteristic size as large as 7 x 10 mm(2), with height of approximately 640 nm, and without any internal support structure. The cells were fabricated from Hoya SD-2 glass and silicon wafers, each with 3 mm thickness to maintain dimensional stability under internal pressure. Bonding was carried out at 350 degrees C and 450 V with an electrode structure that excluded the electric field from the open region. We detail fabrication and characterization steps and also discuss the design of the fill line for access to the cavity.

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“…The centre of the top wafer has a series of 8-mm-long, 15-µm-wide channels that take the helium from the centre filling hole to the rest of the cell. The cell is formed by direct wafer bonding 15 . The resulting structure is an array of boxes spaced 6 µm centre to centre and connected through a planar opening 31.7 nm high.…”

Section: Figure 1 | the Confinement Cellmentioning

confidence: 99%

Coupling and proximity effects in the superfluid transition in 4He dots

et al. 2010

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The superfluid transition in 4 He is associated with the onset of an order parameter that is a macroscopic wavefunction. This is similar to the onset of superconductivity in metals and alloys. Yet, some of the hallmark phenomena that are associated with wavefunctions, and are evident in superconductors, have not been identified in 4 He. Here we report proximity effects on the specific heat and superfluid density of a thin 4 He film in equilibrium with an array of larger boxes of 4 He. Comparison with previous data also enables us, by scaling, to deduce an excess specific heat associated with a collective behaviour of weakly coupled boxes. These effects should be relevant to the understanding of experiments where helium has been studied when confined in packed powders, porous materials or other inhomogeneous confinements, where proximity and collective effects must be present but not readily quantifiable 1,2 . Our work also forms a point of comparison and contrast with the case of superconductors 3,4 , and is relevant to studies of Josephson effects in superfluids, coupling effects in arrays of Bose-condensed atoms 5,6 , and magnetic systems where, because of chemical composition, two separate but interacting ordering transitions take place 7,8 .In the case of superconductors, coupling and proximity effects have been well understood for many years. The large correlationlength amplitude ξ 0 makes coupling between two superconductors easy to achieve. Weak links with dimensions of the order of ξ 0 , which can be a metal, an insulator or another superconductor, enable measurements of the familiar Josephson effects (see for instance ref. 9). With 4 He these effects are much more difficult to achieve because ξ 0 is of the order of interatomic dimensions. Furthermore, weak links and coupling between two regions of 4 He cannot be achieved through any material other than 4 He. We can, however, take advantage of the growth of the correlation length with temperature T and critical exponent ν, ξ = ξ 0 |1 − T /T λ | −ν ≡ ξ 0 t −ν near the transition temperature T λ and construct apertures whereby analogous Josephson effects can be realized 10,11 .We are unaware of any theory that describes the effects on thermodynamic properties of a 'grain' or dot of helium due to a coupling to another dot through a weak link, or, for that matter, how this coupling is affected by the geometry or 'strength' of this link. This question arose while attempting to verify finite-size scaling for zero-dimensional crossover 12 . We had measured the heat capacity of helium in arrays of (1 µm) 3 and (2 µm) 3 boxes linked by channels of 1 µm × 1 µm × 0.019 µm and 2 µm × 2 µm × 0.010 µm respectively. These data did not scale anywhere in the critical region 13 . The lack of scaling is unexpected, because for both twoand one-dimensional crossover, at least for T > T λ , other data do scale 14 . More significantly, an analysis of the zero-dimensional data suggested that the smaller boxes had a higher heat capacity than expected 13 . This might result from ...

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Si wafers uniformly spaced; bonding and diagnostics

Cited by 34 publications

References 12 publications

Specific Heat and Scaling of4HeConfined in a Planar Geometry

Specific Heat and Scaling of4HeConfined in a Planar Geometry

Anodically bonded submicron microfluidic chambers

Coupling and proximity effects in the superfluid transition in 4He dots

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