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A physical model on dipole formation at high-k/SiO2 interface is proposed to study possible mechanism of flatband voltage (VFB) shift in metal-oxide-semiconductor device with high-k/metal gate structure. Dielectric contact induced gap states (DCIGS) on high-k or SiO2 side induced by high-k and SiO2 contact are assigned to dominant origin of dipole formation. DCIGS induced interface dipole is considered to cause VFB shift through charge transfer effect. Based on the proposed model, directions of dipoles at several high-k/SiO2 interfaces are predicted, and magnitudes of dipoles are approximately calculated. Both directions and magnitudes are in agreement with the reported results.

Effects of Gd doping on band gap, band offset, oxygen vacancies, and electrical properties of amorphous HfO2 film have been studied. The results show that Gd incorporation helps increase band gap, conduction band offset and conduction band minimum, and reduce oxygen vacancies simultaneously. Kept at the same physical thickness of 5 nm, Gd-doped HfO2 gate dielectric has a leakage current density of 9.0×10−4 A/cm2 at 1 V gate voltage, one and a half orders of magnitude lower than that of the pure HfO2. Gd doping also enhances the dielectric constant. The capacitance equivalent thicknesses of 0.98 nm and 0.81 nm for HfO2 and Gd-doped HfO2 films, respectively, have been obtained.

In this work, a series of molecules TPE-PA-n (n = 3−11) were designed with classic aggregation-induced emission (AIE) 1,1,2,2-tetraphenylethene (TPE) for self-assembled monolayers (SAMs), which are applied for the detection of trace nitroaromatic compound (NAC) explosives. Phosphoric acid that acts as an anchor is used to connect with TPE through alkyl chains of various lengths. It is found that the alkyl chains play a role in pulling TPE luminogens to aggregate for light emission, which can affect the fluorescence and sensing performance of the SAMs. Ulteriorly, a model is built to explore the influence of the alkyl chain length on the device performance, which is determined by the three effects of the alkyl chain: flexibility, the coupling effect, and the odd−even effect. By comparison, the functional molecules with the chain length of 8 were finally selected and further applied for NAC sensors. By means of fluorescence spectra, the SAM sensor was proved to have good stability, reversibility, selectivity, and sensitivity, and its detection limits for trinitrotoluene, dinitrotoluene, and nitrobenzene were 1.2, 6.0, and 35.7 ppm, respectively. This work provides new ideas for the design and preparation of flexible sensors for trace NAC detection with high performance, low cost, and easy operation.

Articles you may be interested inMechanism of V FB / V TH shift in Dysprosium incorporated HfO 2 gate dielectric n-Type Metal-Oxide-Semiconductor devices J. Vac. Sci. Technol. B 29, 021209 (2011); 10.1116/1.3562974 Physical origin of dipole formation at high-k / SiO 2 interface in metal-oxide-semiconductor device with highk /metal gate structure Appl. Phys. Lett. 96, 152907 (2010); 10.1063/1.3399359Effect of Al-diffusion-induced positive flatband voltage shift on the electrical characteristics of Al-incorporated high-k metal-oxide-semiconductor field-effective transistor Improved high-field reliability for a SiC metal-oxide-semiconductor device by the incorporation of nitrogen into its HfTiO gate dielectric Electrical characteristics of HfO 2 / SiO 2 interface are comprehensively studied to clarify the intrinsic origin of flatband voltage ͑V FB ͒ shift in metal-oxide-semiconductor ͑MOS͒ device with high-k/metal gate structure. A methodology for quantitative extraction of the interface dipole and chargers at high-k/SiO 2 interface is proposed. The dipole and charges at HfO 2 / SiO 2 interface are extracted to be about Ϫ0.38 V and −1.15ϫ 10 13 cm −2 , respectively. This result shows that the high density of negative charges at HfO 2 / SiO 2 interface rather than the interface dipole are the dominant cause of the positive V FB shift in the MOS device with HfO 2 / SiO 2 stack.