The pH-Sensitive Characteristics of Thermal ZrO2 / SiO2 Stacked Oxide Sensors

Abstract

The ZrO 2 / SiO 2 stacked oxides prepared by thermal oxidation were implemented at the temperature of 600 to 900 in ambient oxygen. The transmission electron microscopy (TEM) results indicated that the higher the oxidation temperature the thicker the oxide layer. The total capacitance of corresponding metal oxide semiconductor capacitor is decreased and the equivalent oxide thickness (EOT) is increased. Large shift of flat-band voltages are observed when the ZrO 2 / SiO 2 stacked oxides ElectrolyteInsulator-Semiconductors (EIS) structure is immersed in the pH=2,4,6,8 and 10 buffer solutions, respectively. The hydrogen ion sensitivity of this structure is found up to be 50.6 mV/pH when the oxidation temperature is 900 .

Capacitive Field-Effect EIS Chemical Sensors and Biosensors: A Status Report

“…It is known that the gate-insulator material in the first ISFET was SiO 2 , which is not the best pH-sensitive material, having a low sensitivity, a narrow linear pH range, a relatively high drift, and a large hysteresis (see, e.g., [9,30,31]). Therefore, other oxides, like Al 2 O 3 [32][33][34], Ta 2 O 5 [29,35,36], ZrO 2 [37], HfO 2 [38][39][40][41], CeO 2 [42], Gd 2 O 3 [43,44], Ti-doped Gd 2 O 3 [45], Lu 2 O 3 [46], Nd 2 O 3 [47], Yb 2 O 3 [48], Dy 2 TiO 5 [49], Er 2 TiO 5 [50], PbTiO 3 [51], YTi x O y [52], Tm 2 Ti 2 O 7 [53], and barium strontium titanate (BST) [54][55][56], as well as Si 3 N 4 [32,57] and nanocrystalline diamond (NCD) [58], have been proven as pH-sensitive gate insulators for EIS sensors. Some of the recent results, including the pH-sensitive material used, deposition technique, pH sensitivity, pH range, drift, and hysteresis, are summarized in Table 1.…”

Miniaturized pH‐Sensitive Field‐Effect Capacitors with Ultrathin Ta2O5 Films Prepared by Atomic Layer Deposition

“…However, while providing a stable Si-SiO 2 interface with a low density of states, it suffers from a low pH sensitivity, a restricted linear pH range as well as a relatively large drift and hysteresis. [9,26,27] Therefore, plenty of thin-film high-κ materials (e.g., Si 3 N 4 , [28][29][30] Al 2 O 3 , [30][31][32] Ta 2 O 5 , [1,[33][34][35] ZrO 2 , [36,37] HfO 2 , [38][39][40] CeO 2 , [41] TiO 2 , [42] SnO 2 , [43] Gd 2 O 3 , [44] and barium strontium titanate, [45,46] just to name a few) have been studied as pH-sensitive gate insulators in electrolyte-gated field-effect devices, in particular, in EISCAPs. These films were deposited either directly on the Si substrate to replace the SiO 2 or on a SiO 2 layer as stacked gate insulators.…”

Comparison of ZnO, Al2O3, AlZnO, and Al2O3-Doped ZnO Sensing Membrane Applied in Electrolyte-Insulator-Semiconductor Structures

“…A detailed EIS structure containing membranes is illustrated in Figure 1. to replace SiO2 as the sensing membrane [5][6][7][8]. These dielectrics can have better sensing performance owing to effective electric field crossing in the oxides and high thermal stability.…”

“…In a conventional EIS device, the dielectric layer is SiO 2 , which has the disadvantages of ineffective electric field crossing, low capacitance, and threshold voltage instability. Recently, various high-k dielectrics, including Ta 2 O 5 , HfO 2 , Y 2 O 3 , and ZrO 2 , have emerged to replace SiO 2 as the sensing membrane [5][6][7][8]. These dielectrics can have better sensing performance owing to effective electric field crossing in the oxides and high thermal stability.…”