An improved laminated enzyme containing membrane for polarographic sensors and methods of making these membranes are disclosed. The laminated membrane comprises an outer, support layer having pores therein of greater than about 300 angstrom units in diameter and this outer membrane has a pore density of less than 6.times.10.sup.8 pores/cm.sup.2. The porosity of the outer membrane may be on the order of 0.001-0.2%. An enzyme layer is interposed between the support layer and an inner, barrier layer; the latter positioned near the working electrode of the polarographic cell. The enzyme layer comprises a buffer solution dispersed therein wherein the molarity of the buffer solution is between about 1.times.10.sup.-6 to 0.1 M. The enzyme layer is highly dense as measured by a molar response ratio of ferrocyanide:H.sub.2 O.sub.2 of less than about 0.05.
A method for forming a strained layer of semiconductor material, e.g., silicon, germanium, Group III/V, silicon germanium alloy. The method includes providing a non-deformable surface region having a first predetermined radius of curvature, which is defined by R(1) and is defined normal to the surface region. The method includes providing a first substrate (e.g., silicon wafer) having a first thickness. Preferably, the first substrate has a face, a backside, and a cleave plane defined within the first thickness. The method includes a step of overlying the backside of the first substrate on a portion of the surface region having the predetermined radius of curvature to cause a first bend within the thickness of material to form a first strain within a portion of the first thickness. The method provides a second substrate having a second thickness, which has a face and a backside. The method includes a step of overlying the face of the second substrate on a portion of the face of the first substrate to cause a second bend within the thickness of material to form a second strain within a portion of the second thickness. A step of joining the face of the second substrate to the face of the first substrate form a sandwich structure while maintaining the first bend in the first substrate and the second bend in the second substrate. Preferably, joining occurs using a low temperature process such as plasma activated bonding or the like.
