Adsorption of self-assembled monolayer on Cu(111): First-principles study

The density function theory is used to explore the structures of alkyl-thiolate (RS, R=CH3, CF3) monolayer on the Cu(111) surface. By performing the total energy calculations for RS at three possible adsorption sites (fcc, hcp, bridge) with five different coverages (1/12, 1/9, 1/6, 1/4, 1/3), we obtained the stable adsorption configurations of the Cu–RS system. Especially, the effect of Van der Waals interaction on the adsorption configurations was studied by the DFT-D2 method. The work functions for Cu–RS (R=CH3, CF3) systems were calculated, we find that the CH3S adsorbed on the Cu(111) surface decreases the metal work function remarkably, and the work functions strongly depend on the coverage. In the case of the Cu–CF3S system, the results are just the opposite. Thus, controlling the kind and coverage of the surface adsorbates would be an effective technique to tune the work function of the metal.

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Measuring The Work Functions Of PVD TaN, TaSiN And TiSiN Films With A Schottky Diode CV Technique For Metal Gate CMOS Applications

MRS Proceedings ◽

10.1557/proc-745-n3.2 ◽

2002 ◽

Vol 745 ◽

Cited By ~ 5

Author(s):

James Pan ◽

Christy Woo ◽

Minh-Van Ngo ◽

Bryan Tracy ◽

Ercan Adem ◽

...

Keyword(s):

Work Function ◽

Nitrogen Content ◽

Schottky Diode ◽

Metal Gate ◽

Promising Candidate ◽

Auger Analysis ◽

Metal Work Function ◽

Work Functions ◽

Metal Work

ABSTRACTThe metal gate process becomes a promising candidate for sub-65nm CMOS, due to the elimination of polysilicon depletion effects, and the possibility of adjusting the CMOS threshold voltage without more threshold implants. Our goal is to process mteal films with tunable work functions, in order to meet the demand of sub-65nm metal gate CMOS.PVD TaN films are deposited with various processing conditions. Auger analysis shows that by changing the nitrogen flow rate and the plasma power, the nitrogen content in the TaN films can be adjusted. In order to accurately determine the work function of these TaN materials, we have developed a Schottky Diode CV technique (or Metal-Silicon CV, or MS-CV). This approach not only improves the accuracy of the metal work function measurement, compared with the traditional MOS-CV technique (which is affected by the thickness and quality of the oxide), but also simplifies the fabrication.With the MS-CV's, we have successfully measured the work functions of Ni and Co, and compared the data with published references. The work function of PVD TaN actually decreases with higher nitrogen content, according to the Auger data and the MS-CV measurement, ranging from 3.42 – 4.20 Volts. The MS-CV technique is shown to be independent to the size of the capacitors, and is little affected by the measurement frequency. By changing the frequency from 100KHz to 1MHz, the error in the work function is less than 50mV.

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Effect of Gate Metal Work Function on Leakage Current in Single Pocket FDSOI 28 nm Transistor

2021 10th IEEE International Conference on Communication Systems and Network Technologies (CSNT) ◽

10.1109/csnt51715.2021.9509715 ◽

2021 ◽

Author(s):

Aryan Kannaujiya ◽

Sandhya Kannaujiya ◽

Rajeev Kumar Chauhan

Keyword(s):

Work Function ◽

Leakage Current ◽

Metal Work Function ◽

Metal Work ◽

28 Nm

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Two-terminal vertical thyristor using Schottky contact emitter to improve thermal instability

Nano Futures ◽

10.1088/2399-1984/ac3bd4 ◽

2021 ◽

Author(s):

Min-Won Kim ◽

Ji-Hun Kim ◽

Jun-Seong Park ◽

Byoung-Seok Lee ◽

Sangdong Yoo ◽

...

Keyword(s):

Thermal Stability ◽

Work Function ◽

Thermal Instability ◽

Schottky Contact ◽

Memory Cell ◽

Cross Point ◽

Operation Temperature ◽

Metal Work Function ◽

Metal Work ◽

Contact Metal

Abstract In a two-terminal-electrode vertical thyristor, the latch-up and latch-down voltages are decreased when the memory operation temperature of the memory cells increases, resulting in a severe reliability issue (i.e., thermal instability). This study fundamentally solves the thermal instability of a vertical-thyristor by achieving a cross-point memory-cell array using a vertical-thyristor with a structure of vertical n++-emitter, p+-base, n+-base, and p++-emitter. The vertical-thyristor using a Schottky contact metal emitter instead of an n++-Si emitter significantly improves the thermal stability between 293 and 373 K. Particularly, the improvement degree of the thermal stability is increased significantly with the use of the Schottky contact metal work function. Because the thermal instability (i.e., degree of latch-up voltage decrement vs. memory operation temperature) decreases with an increase in the Schottky contact metal work function, the dependency of the forward current density between the Schottky contact metal and p+-Si based on the memory operation temperature reduces with increase in the Schottky contact metal work function. Consequently, a higher Schottky contact metal work function produces a higher degree of improvement in the thermal stability, i.e., W (4.50 eV), Ti (4.33 eV), Ta (4.25 eV), and Al (4.12 eV). Further research on the fabrication process of a Schottky contact metal emitter vertical-thyristor is essential for the fabrication of a 3-D cross-point memory-cell.

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