Step-flow growth of nanolaminate Ti3SiC2 epitaxial layers on 4H-SiC(0 0 0 1)

Abstract

Epitaxial Ti 3 SiC 2 (0001) films were deposited on 4° off-cut 4H-SiC(0001) wafers using magnetron sputtering. A lateral step-flow growth mechanism of the Ti 3 SiC 2 was discovered by X-ray diffraction, elastic recoil detection analysis, atomic force microscopy, and electron microscopy. Helium ion microscopy revealed contrast variations on the Ti 3 SiC 2 terraces, suggesting a mixed Si and Ti(C) termination. Sirich growth conditions results in Ti 3 SiC 2 layers with pronounced {11 2 0} faceting and off-oriented TiSi 2 crystallites, while stoichiometric growth yields truncated {1 1 0 0} terrace edges.Keywords: Sputtering, atomic force microscopy (AFM), helium ion microscopy (HIM), transmission electron microscopy (TEM), crystal structure  Corresponding author. Tel.: +46 13281062; e-mail: kribu@ifm.liu.se. 2Silicon carbide (SiC) is a wide bandgap semiconductor with high breakdown field and high thermal conductivity; it therefore finds applications in devices and sensors for operation at high power and high temperature [1][2][3][4]. In such electronic device applications, a challenge is the formation of ohmic contacts to the SiC, as well as the durability of the contacts when operated at elevated temperatures. High-temperature annealed Ti/Al contacts on p-type SiC have been reported to form Ti 3 SiC 2 [5-8], which is suggested to contribute to the ohmic behavior of the contacts [9][10][11].Formation of Ti 3 SiC 2 and subsequent ohmic behavior has also been reported for hightemperature annealed Ti-based contacts on n-type SiC [12,13]. Here, we investigate the growth of Ti 3 SiC 2 thin films on 4° off-cut 4H-SiC using DC magnetron sputtering from three sources. We find that the Ti 3 SiC 2 grows epitaxially by a step-flow mechanism determined by the existing surface steps of the SiC substrate, in the absence of screw dislocations. The Ti 3 SiC 2 layers exhibits a mixture of half, full, and multiple unit cell high steps. Si-supersaturation growth conditions results in growth of steps with {11 2 0} faceting, while stoichiometric conditions yield {1 1 0 0} step truncation. Helium ion microscopy studies reveal differently terminated terraces. (0001) The substrates were then blown dry in N 2 gas and immediately loaded into the ultrahigh vacuum magnetron sputtering system. The substrates were heated to the deposition temperature of 800 °C, and left to stabilize at that temperature for 1 h. 4H-SiCImmediately before deposition the substrates were plasma etched for 30 minutes to remove any surface oxide on the SiC. Plasma etching was performed through operating the Ti-target at 25 mA in high purity Ar discharges, while applying a negative bias of -50 V to the substrate. The Ti 3 SiC 2 films were grown using high purity C, Si, and Ti targets as described elsewhere [17,20] As-deposited films were characterized by θ-2θ X-ray diffraction (XRD) measurements, performed in a Philips PW 1820 diffractometer with Cu Kα radiation, operated at 40 kV and 40 mA. The instrument was aligned using the (0004) SiC substrate peak giving an o...

Growth and characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001)

“…The substrates were heated to the deposition temperature of 800 °C and left to stabilize at that temperature for 1 h prior to deposition. Immediately before deposition the substrates were plasma etched for 30 minutes through operating the Ti-target at 25 mA in high purity Ar discharges, while applying a negative bias of -50 V to the substrate, in order to remove any remaining surface oxide on the SiC substrate [12]. Ti 3 GeC 2 films were grown by DC magnetron sputtering, using high purity C, Ge, and Ti targets, using an experimental setup described elsewhere [25].…”

“…In recent publications, we have reported on the ohmic contact properties of sputter-deposited Ti 3 SiC 2 on 4H-SiC(0001), and investigated the step-flow growth mode of epitaxially grown Ti 3 SiC 2 layers on SiC [11,12].…”

Epitaxial growth and electrical transport properties of Cr2GeC thin films

“…for Ti 3 SiC 2 contacts to SiC. [20][21][22] As thin films, the close relatives of Cr 2 GeC, Ti 2 GeC, [23][24][25][26] V 2 GeC, 27,28 and Cr 2 AlC [29][30][31][32][33][34] have all been investigated. From a potential technological viewpoint, the latter two are particularly interesting since they can be grown at a relatively low substrate temperature (450 • C), 27,29 which is essential for deposition onto technologically relevant substrates, such as steels.…”

Single-step synthesis process of Ti 3 SiC 2 ohmic contacts on 4H-SiC by sputter-deposition of Ti

“…This 12 family exhibits an unusual combination of metallic and ceramic-like properties 16 such as high-13 temperature stability and high electrical conductivity. Ti 3 SiC 2 thin films are commonly grown by 14 physical vapor deposition, primarily sputtering from elemental 17,18 or compound targets. 19 However, 15 growth of this phase on 4H-SiC was reported to still require high temperature rapid thermal annealing 16 to exhibit Ohmic properties.…”