InN materials have been attracting a lot of attention for its prominent application in electronic and optical devices

compared with GaN and AlN

InN has smaller effective mass and higher electron drift velocity.However

the growth difficulties due to low growth temperature and lack of lattice-matched substrate restricted the evolution of InN-based devices

more and more efforts are made in efficiently deposit InN films with better quality.InN films were synthesized on the(0001) sapphire substrates at different growth temperatures by metal organic chemical vapor deposition(MOCVD)

the growth source materials are trimethy lindium(TMI)

trimethy lgallium(TMG) and ammonia(NH

3

).The physical properties of the films were characterized by a series of measurements.We fully studied the characteristic of InN films by various methods

such as X-ray diffraction(XRD)

atomic force microscope(AFM)

X-ray photoelectron spectroscopy(XPS) and Raman measurements.It's well known that the growth temperature is one of the most important parameters in growth of InN films

so in our study

we focus our attention mainly on the effect of growth temperature.It was found that 600℃ is a suitable growth temperature for InN films

the suitable temperature can inhibit the surface segregation phenomenon of In on the surface of InN films.But at a lower or higher temperature it will lead to a surface segregation of In on the InN films.The crystalline quality and morphology of the surface for the sample without surface segregation have been improved compared with the samples with surface segregation.In addition

it was also found that the residual strain in InN films increased with increasing growth temperature by Raman analysis

the E

2

(high) model frequency shift toward high frequency with increasing growth temperature

and this shift is due to the presence of residual thermal strain in the InN film.When the growth temperature is lower

the residual thermal strain came into being due to the different thermal expand coefficient between the epitaxial-film and the sapphire substrate.The residual thermal strain is biaxial strain

which can be expressed as:ε

xx

=(

T

g

-

T

r

)(α

sub

-α

film

)

T

g

T

r

are the growth and room temperature

α

sub

α

film

are the thermal expand coefficient of sapphire substrate and InN film

respectively.The relation between E2(high) model frequency and residual thermal strain can be expressed as:ω=20ε

xx

+479(cm

-1

)

which fit from the result of Raman analysis

where ω is the E

2

(high) model frequency

and ε

xx

is the residual biaxial thermal strain.