Surface group modification and carrier transport properties of layered transition metal carbides (Ti₂CT_x, T: –OH, –F and –O)

Abstract

In spite of recent significant research into various two-dimensional (2D) materials after the emergence of graphene, the development of a new 2D material that provides both high mobility and an appropriate energy band gap (which are crucial for various device applications) remains elusive. In this report, we demonstrate that the carrier transport behaviour of 2D Ti2CTx, which belongs to the family of 2D transition metal carbides and nitrides, can be tuned by modifying the surface group Tx (-OH, -F, and -O). Our results show that 2D Ti2C(OH)xFy and Ti2COx films can be obtained via simple chemical treatment, thermal annealing, and mechanical exfoliation processes. For the first time, we study the carrier transport properties of 2D Ti2CTx field effect transistors (FETs), obtaining the high field effect carrier mobilities of 10(4) cm(2) V(-1) s(-1) at room temperature. The temperature dependent resistivity of the Ti2COx film exhibits semiconductor like Arrhenius behaviour at zero gate voltage, from which we estimate the energy gap of 80 meV. One interesting feature of the FETs based on transition metal carbides is that the field effect mobility at room temperature is less sensitive to the measured transport gaps, which may arise from the dominant charge transport of activated carriers over the narrow energy gaps of the transition metal carbides. Our results open up the possibility that new 2D materials with high mobilities and appropriate band gaps can be achieved, and broaden the range of electronic device applications of Ti2CTx films.

Effect of Synthesis on Quality, Electronic Properties and Environmental Stability of Individual Monolayer Ti3C2 MXene Flakes

“…[4,6] Yet, the applications of this new family of the 2D materials in electronic devices, such as transistors and sensors, remain underdeveloped. [1,[12][13][14] One of the reasons for this is the lack of experimental data on electronic properties of single-and multi-layer MXenes. Electronic properties of the most widely studied MXene, Ti 3 C 2 T x , were measured for bulk, [4,15] thin film, [3] and individual multilayer particles, [16] and-only recently-individual flakes [17] (see Table S1 in the Supporting Information for a comparison).…”

Electronic properties and applications of MXenes: a theoretical review

“…Experimentally, MXenes have already found applications as transparent conductors [18][19][20], field effect transistors [21], supercapacitors [22][23][24], Li ion batteries [25,26], electromagnetic interface shielders [27], fillers in polymeric composites [28], hybrid nanocompositites [29], purifiers [30,31], dual-responsive surfaces [32], suitable substrates for dyes [33], catalysts [34,35], promising materials for methane storage [36], and photocatalysts for hydrogen production [37], as well as being ceramic biomaterials with high photothermal conversion efficiency for cancer therapy [38]. Theoretically, many applications have been proposed for MXenes in electronic [39][40][41][42][43], magnetic [44][45][46][47][48], optical [49,50], thermoelectric [51][52][53][54][55][56], and sensing devices [57], as well as being new potential materials for catalytic and photocatalytic reactions [58][59][60]…”

Thermoelectric Performance of the MXenes M2CO2 (M = Ti, Zr, or Hf)

“…8 Ti 2 CO 2 has a narrow band gap of 0.17-0.44 eV, 9-11 thus being interesting for thermoelectric applications, and shows a high carrier mobility. 12 Zr 2 CO 2 and Hf 2 CO 2 share many properties with Ti 2 CO 2 because of their structural and compositional similarity. 10 First principles calculations predict high Seebeck coefficients (1100 µV/K and 2000 µV/K, respectively) 8 and power factors 10 for Ti 2 CO 2 and Sc 2 C(OH) 2 at 100 K. However, these electronic quantities are not sufficient to determine the thermoelectric efficiency, since the lattice contribution to the thermal conductivity also influences the figure of merit.…”